your son eats better than most 15-year-olds let me tell you. If he likes fish, chicken, red meat (but no pork? hmmm better have a doc check that out

) and gets his green veggies I'd say he's doing rather well. Personally I don't bother with creatine, I think he'd be fine with a good multi vitamin and ample protein intake.
I think all teenagers are moody, just part of the natural progression. I wouldn't worry about a supplement to really
improve his mood per say, but who knows, with a good diet and some added muscle his mood may improve naturally.