Is this balanced?

I am working on making a tanking focused subclass for fighter. I wanted to ask if this is balanced or not;

Juggernaut's plate

You can spend a long rest and adequate materials to attempt to modify a set of heavy armour into juggernaut plate. Juggernaut plate is massive, Heavy, imposing, and immensely durable. It is heavy armour with a strength requirement of 16 and a constitution requirement of 14. If you fail to meet the strength requirement, your speed is halved and you cannot jump. If you do not meet the constitution requirement you must make a constitution save(Dc 12) every hour or gain a level of exhaustion. Juggernaut plate has a base AC of 20 and reduces all damage taken by your PB, but imposes disadvantage on all dexterity checks and saves. Only a juggernaut can wear this armour.

Armour smith

You gain proficiency with smith's tools and your proficiency bonus is doubled when making or maintaining armour.

Bull rush

When you move more than 10 ft towards a target you can both make an attack and throw them 10 ft in any direction

Body block

Whenever an ally within reach becomes the target of an attack, you can take a reaction to put yourself in the way, taking the damage for them. When you do this, the attack automatically hits and the damage from it cannot be reduced in any way.

Steel titan

Your size increases by one category(Med->large, small->med)

Your reach is increased by five ft.

You have advantage on STR. checks and saves.

Your health is increased by 2 for every fighter lvl you have

You cannot wear any armour other than juggernaut plate and all clothes have to be specially tailored to fit you.

Indomitable beast

You gain the following features:

You are immune to critical hits.

Your armour becomes indomitable juggernaut armour and has a base AC of 28, reduces all damage by twice your PB, and gives disadvantage on all dex saves and checks.

You cannot be restrained, stunned, or incapacitated and you are immune to the frightened condition.

You have advantage on death saving throws.

What levels are all these for?

No, it's not balanced that capstone is way too powerful. Similarly the Juggernaut Plate is too powerful at level 3 and not powerful enough at level 15.

Bull rush is either too powerful or not powerful enough depending on what action is required to make the attack it provides and whether that attack also deals damage.

Steel titan ok but in some contexts could be a problem. In a pre-made dungeon, often a Large creature doesn't fit on the map and either has to Squeeze which is really bad if you are in combat or ends up creating cover for the enemies. Being a Large creature can also be in issue for things like Flying Carpets, so being Large is often not an advantage which is why many classes / features just give it as an option to temporarily become large. 

I agree with what Agilemind said. There's a reason why Goliaths, Centaurs and Firebolg are Medium species even though lore-wise they should be Large.

It is heavy armour with a strength requirement of 16 and a constitution requirement of 14. If you fail to meet the strength requirement, your speed is halved and you cannot jump. If you do not meet the constitution requirement you must make a constitution save(Dc 12) every hour or gain a level of exhaustion. Juggernaut plate has a base AC of 20 and reduces all damage taken by your PB, but imposes disadvantage on all dexterity checks and saves. Only a juggernaut can wear this armour.

This section would make sense if someone else could try to wear that armor, but since it's exclusive to your subclass, the requirements do nothing besides forcing the player to build their stats in a specific way, which will bring them nothing but frustration. Either allow someone else to wear the armor, or get rid of the requirements.

Also, forbidding Resistances and Immunity for Body Block makes no sense. I would get rid of that as well.

thanks for the feedback!

This is the revised version;

3rd LVL: Juggernaut's plate

You can spend a long rest and adequate materials to attempt to modify a set of heavy armour into juggernaut plate. Juggernaut plate is massive, Heavy, imposing, and immensely durable. Juggernaut plate has a base AC of 20 and imposes disadvantage on all dexterity checks. Only a juggernaut can wear this armour.

3rd LVL: Armour smith

You gain proficiency with smith's tools and your proficiency bonus is doubled when making or maintaining armour.

5th LVL: Bull rush

once per turn when you move more than 10 ft towards a target you can both make an attack and throw them 10 ft in any direction when you make an attack. 

10th LVL: Body block

Whenever an ally within reach becomes the target of an attack, you can take a reaction to put yourself in the way, taking the damage for them. When you do this, the attack automatically hits.

15th LVL: Steel titan

Your size increases by one category(Med->large, small->med)

Your reach is increased by five ft.

You have advantage on STR. checks and saves.

Your health is increased by your STR modifier for every fighter lvl you have

you gain expertise and advantage on all intimidation checks.

You cannot wear any armour other than juggernaut plate and all clothes have to be specially tailored to fit you.

18th LVL:Indomitable beast

You gain the following features:

You are immune to critical hits.

You cannot be restrained or incapacitated and you are immune to the frightened condition.

You have advantage on death saving throws.

Some fine adjustments to make:

Quote from the_scalebrand >>

3rd LVL: Juggernaut's plate

You can spend a long rest and adequate materials to attempt to modify a set of heavy armour into juggernaut plate. Juggernaut plate is massive, Heavy, imposing, and immensely durable. Juggernaut plate has a base AC of 20 and imposes disadvantage on all dexterity checks. Only a juggernaut can wear this armour.
There should be a cost in raw material with a gold price included as well. (for example 50gp worth of iron)

3rd LVL: Armour smith

You gain proficiency with smith's tools and your proficiency bonus is doubled when making or maintaining armour.

5th LVL: Bull rush

once per turn when you move more than 10 ft towards a target you can both make an attack and throw them 10 ft in any direction when you make an attack. 
I would rephrase this as "10ft or more", otherwise it's unclear if exactly 10ft is enough. You could have a player say "I move 10 feet and 1 inch".
You should also put a size limit. No matter how strong your character is, you're not gonna "throw" a Greatwyrm.

10th LVL: Body block

Whenever an ally within reach becomes the target of an attack, you can take a reaction to put yourself in the way, taking the damage for them. When you do this, the attack automatically hits.

15th LVL: Steel titan

Your size increases by one category(Med->large, small->med)

Your reach is increased by five ft.

You have advantage on STR. checks and saves.

Your health is increased by your STR modifier for every fighter lvl you have

you gain expertise and advantage on all intimidation checks.
You can't get Expertise without Proficiency first, that's why features that give Expertise also mention "if you lack Proficiency, you gain it too."

You cannot wear any armour other than juggernaut plate and all clothes have to be specially tailored to fit you.

18th LVL:Indomitable beast

You gain the following features:

You are immune to critical hits.
Worded like this, it could be argued that you take no damage on a crit. I would write it like Adamantine armor: "If you take a critical hit, it becomes a normal hit instead".

You cannot be restrained or incapacitated and you are immune to the frightened condition.
Immunity to the Incapacitated condition is game-breaking, many other conditions depend on it. Only 8 monsters have this immunity across all WotC material, and they're all special in some way. I would replace it with Stunned immunity and/or Paralyzed.

You have advantage on death saving throws.

Steel Titan is now also unbalanced, it grants way too many additional hit points.

You have not addressed the problems with becoming permanently Large size.

You have not addressed the problems with Jugernault plate scaling compared to e.g. the magical armour an Artificer can create.

It is unclear how many attacks Bull Rush applies to, it is not clear how "throw" works mechanically - e.g. do you need to grapple them first? does it follow the rules for the Shove action. 

Fixes:

3rd LVL: Armour smith

You gain proficiency with smith's tools and your proficiency bonus is doubled when making or maintaining armour.

3rd LVL: Juggernaut's plate

When you complete a long rest, you can use your Smith's Tools to modify a set heavy armour into juggernaut plate. Juggernaut plate is massive, Heavy, imposing, and immensely durable. Juggernaut plate has a base AC of 20 and imposes disadvantage on all dexterity checks. Only a juggernaut can wear this armour.

5th LVL: Bull rush

When you move at least 10 feet towards a target, then hit that target with an attack, you hurl that creature 10 feet in a direction of your choice.

10th LVL: Body block

Whenever an ally within reach becomes the target of an attack, you can take a reaction to put yourself in the way, taking the damage for them. When you do this, the attack automatically hits.

15th LVL: Steel titan

You can use your Bonus Action to increase your size by one category (Med->large, small->med). This change lasts for 1 hour or until you choose to end it (no action required). While you are in your larger form, your reach is increased by 5 ft and you have advantage on Strength checks and saves.

You can use this ability a number of times equal to your Strength modifier, you regain all uses when you finish a long rest.

15th LVL: Fearsome Resilience.

Your maximum hp is increased by 2 for each fighter level you have. You have advantage on all intimidation checks, and can add your Strength modifier in addition to your Charisma modifier to these checks. 

18th LVL:Indomitable beast

You gain the following features:

You are immune to critical hits.

You cannot be restrained or incapacitated against your will, and you are immune to the frightened condition.

You have advantage on death saving throws.