Hi Thomas, looking good , about your questions:
Is it okay if the return edges are gone from the upper opening on the forearms? Yes Its OK
Again the chest seems a tiny bit big, especially on the left side in the first photo, maybe strapping it down should fix it.
You can try strapping it down or trimminr a little bit.
One last thing, is my brown strap too short? It does this on both sides, it just falls short of the edge of the forehead decal should end.
It's just right
keep on doing a great job , I think your next project is going to be your dad's armor
cheers