In my opinion. If you hear warning bells, you should listen to them.
I have to agree. Whatever is going on with him, there isn't an obvious excuse for it, and maybe now that you are there with him, he is just showing his true colours. I'm so sorry to say that. But the things you describe are very much like my ex-boyfriend who was very sweet to begin with, then slowly raveled out into a psycho who was very controlling, said horrible things about my friends and family, and basically just treated me like sh*t, and I thought I knew him, too.
And you have your son with you, who shouldn't be subjected to dealing with someone who is clearly unstable. My biggest pet peeve is inconsistent people - those who are sweet as sugar one day, then act like they don't even know you or care about you the next. No one needs that in their life. Someone who truly loves you will treat you with respect, caring, and tenderness -- not apathy or disdain, especially when someone you knew passed away. My ex did the exact same thing to me when a friend from college passed away. He was so rude and uncaring, and basically said the person meant nothing to me, which is what your DF did to you. How should he know how you felt about someone that you knew before he came along? It's just not right to treat someone like that.
As far as my DH goes, we might disagree sometimes, but we never say horrible things to each other or throw things or act like jerks to one another. An argument or heated discussion about who moved the phone charger would be just that - not some blown out of proportion temper tantrum. If he had acted that way after I moved in with him, I would've gone back to America. No one should have to deal with that, especially after they just gave up everything they had and everyone they knew so that they could be with each other. As you have said, the longer you are here, the harder it will be to leave. I think you should get out now, while you haven't been gone too long, and pick up the pieces of your life. You deserve better and so does your son. You have family and friends who love you and will be so happy to have you back.
I'm so sorry it turned out like this. Unfortunately in most long distance relationships, you don't get to find out who your partner really is until after you are living with them and get to spend each day with them. All you can do is trust that it will be what you wanted, but sometimes, it doesn't turn out that way. But if you had never given it a shot, then you never would've known. Don't kick yourself. Just take everything into consideration, and make a decision based on what is best for you and your little boy. Hugs to you, A.