Having the same problem, I'm a bit of a newb to Forge although I have used it on previous versions.
I updated my sons Minecraft to latest 1.12 on a MacBook Pro, downloaded older MC 1.7.10 version which runs great.
My son wanted to play MC Helicopter MOD so I downloaded Forge 1.7.10, again installed OK.
When I try to launch Forge 1.70.10 I also get the Game Crash screen.