Toxic relationships

So me and my girlfriend (soon to be boyfriend) had been dating for almost a year. We're both 16, but he's going through a tough time because he wants to become a guy. I have absolutely no problems with this and I fully support him and still love him. But since he started identifying as a guy he's been changing, but not in a good way. He's become really possessive and gets angry really easily. I tell him when he gets angry and that I don't like it because it makes me feel really bad, but anytime I talk about how I'm feeling, suddenly it "all about me". He makes me feel really bad about myself, I never get to spend much time with my family or friends and if I don't instantly reply to his texts or calls he gets moody and in in the wrong, even if I physically couldn't reply or answer. There was some other stuff too but I won't go into too much detail. I broke up with him because my best friend had been telling me that it seemed like emotional abuse from her perspective because she knows all the ins and outs of what had been going on. But we talked it through the other day and we're back together, in just really scared he is going to be exactly like he was last time, but I love him so much and I honestly don't want to be without him. I missed him like crazy and I just need some advice on how to approach it if things start to get bad again. So ladies, opinions?