my captives were ready to cut me up and throw me into a furnace XD . or at least that is what my prescription told me . so I didnt wait for them to give me water lol .

If you assume you're not going to take more than 20 damage at a time, and if your Con is 14 or 15, you already have a 13/20 chance of making your saving throw.  If your proficiency bonus is +2 and you take Resilient (Con), that goes up to 3/4; when you hit 5th level, it becomes 4/5.  If you go for War Caster instead, you have a 351/400 chance of making your save (slightly better than 7/8).  If you only have a Con of 12 or 13, those probabilities change to 3/5, 7/10, 3/4, 21/25 and 4/5, respectively. 

Not sure about your number in the case of advantage on the CON saving throw.

Having advantage on a saving throw is equivalent to having a bonus of +4. If you are to beat a DC 15 the chances are:

1) Advantage with +0 modifier: 51 %

2) Advantage with +2 modifier: 64 %

3)  +2 modifier: 40 %

4)  +4 modifier: 50 %

5)  +5 modifier: 55 %

So, Resilient (CON) becomes equivalent to War Caster from level 9 (proficiency +4), and overcomes it at level 13 (proficiency +5).

YES MAAATH !!!! :D 
Thank you for the advice 

If you need to roll a 20+ the prof bonus is not only better but essential, however when you need to roll less than 20, advantage is probably better as you are likely to roll one low roll (which will may fail with the prof bonus) and one high roll which will likely succeed without it. 

One other reason to take war caster is it's spell opportunity attack. This is quite the fun combo with booming blade.

but how many times a creature is gonna run away from a caster ? 

Quote from HaLwAsA >>

but how many times a creature is gonna run away from a caster ? 

thats a darn good spell !!!

Command also works, just choose Flee

No I think it does.
Willing movement to me is a creature using its own movement speed "their own feet or wings" to move away. they turn around and exposing their backs to you.
None Willing movement is they are grappled for example or got pushed back using a spell similar to thunder wave. 

I am not sure about the Booming Blade thing I cant remember it.
if its a spell then you cant cast it except if you have the feat. 
if its a spell with one action and it says as part of casting the spell you make one weapon melee attack then you do just that.

PS: Every DM has the final saying in their table :D .

Quote from HaLwAsA >>

I am not sure about the Booming Blade thing I cant remember it.
if its a spell then you cant cast it except if you have the feat. 
if its a spell with one action and it says as part of casting the spell you make one weapon melee attack then you do just that.

PS: Every DM has the final saying in their table :D .

so whats the thing here I dont get it... Until the next turn if they willingly move they take damage.
well one ruling "if you stretch it" I guess would say that the attack of opportunity that casted the spell the target was in Mid movement or Already moving so thats why it doesn't activate? 
but I think it activate just like a sentinel feat or smite or something like that.

On topic, I've seen math equating advantage to +3-4. If you use Resilient to get to an extra +1 to your CON mod at creation, it equals/beats War Caster as early as +3 proficiency.

On Warcaster w/booming blade: I played a tempest cleric with this combo from 1-17 in PotA and AL. It was amazing. Due to the nature of booming blade, I only recommend it for classes with one attack (casters and rogues), who have survivability or movement (rogue, cleric). If you're going for a melee combatant who is not in animal form, I would recommend switching to Nature cleric. Heavy armor, shillelaghs, and booming blade (magic init or multiclass) is a nice combo. 

sadly RAW and RAI the magic initiative you can only chose one class and take some spells from them and use their spell casting ability state.

Quote from Brian_Avery >>

Is Booming Blade one of the cantrips from Sword Coast Adventurer's Guide that only Sorcerers, Warlocks, or Wizards can use?