what in tarnation sam 

Thunderwave: coincidentally is also my Mountain Dwarf characters band name. 

This spell needs clarification on "where" that 15 foot cube appears... 

is it a 15 foot cube around you, with you in the center?

is it a 15 foot cube adjacent to you (in front? beside? etc)

can you adjust where the 15 foot cube is (5 feet over you, a corner on the side of you, etc)

Is it up to you where the cube goes?

The range is "Self (15 ft. cube)". The text references "Each creature in a 15-foot cube originating from you" which to me explicitly says that the cube is centered on you. It certainly could be clearer though.

I would agree with you, but I have seen it played out differently at different tables.

And it looks like I'm wrong. According to Jeremy Crawford, Thunderwave follows the general rules on cubes, where the point of origin is on the face of the effect.

This is valid:
 XXX
CXXX
 XXX
This is not:
XXX
XCX
XXX

I guess that is that then. Could use a bit of errata to clarify the point perhaps.

I'm kind of torn on Thunderwave. By RAW, the spell is more flexible in its application in that the caster can be choosier about what area they effect with the spell as apposed to just being centered on themselves. At the same time, it kind of makes sense that it would be centered specifically on the caster and should use the sphere which has its point of origin centered on the caster. Alternatively, make it a 15 ft cone like Burning Hands (another 1st level spell) and take the ambiguity out.

I had a question. Lets say i cast thunderwave as a second level spell. Is the damage increase just 1 d8 or 1 d8 per creature hit?

each creature takes 2d8 base, so casting at a higher level will make it 3d8 for each creature and so one

Casting Spellword is:

Allimnius Airvidium

According to the PHB (spellcasting chapter), a cube area of effect has the point of origin on a surface of the cube, not in the center. So the cube would appear in front of you and would be 15 ft on each side. That being said, I guess you and your DM could agree to modify this at your table.

I imagine the dm well decide or its  in front of you 

You have to be adjacent, so...

CCCX

CCC

CCC

Or

CCC

CCCX

CCC

Or

CCC

CCC

CCCX

If you use Thunderwave to push creatures through difficult terrain (like that caused by Spike Growth), do they still get pushed 10 feet, or does it get halved to 5 feet?

10ft, think of difficult terrain as in walking or running, whereas if you were Force Pushed by a Jedi it wouldn’t be the same. 

does this spell give a crap who those creatures are or do you hurt your buddies too when casting this? (I'm guessing the latter.)

Hurts and pushes everyone but the caster

k thanks

If you need to use the spell in an area with your allies, you can use the Careful Spell metamagic if you're a sorcerer. They'll still take half damage, but they won't be pushed. There's also the Sculpt Spell feature for Evocation wizards that completely negates friendly fire