Why not? He's 15, if the violence is what makes you ask, stop being silly. He can handle it. Worth to mention is that there are microtransactions in the game, meaning it sells unecessary crap for money. Make sure he doesn't buy a lot of that, at least.
No, I really dont think so. Stay away from your son from this game. It's really not a game of teenager, I also not give permission to my son to play this game, you can buy many good games for you son From reecoupons.com/categories/back-to-school, I also bought games for my son from there. I hope you will definitely find good games for your son too.
What a bunch of horseshit. And learn to spell, you're a parent for god's sake.