I have been right where you are now, exactly in that same position and before I give any advice I'm going to say that I'm extremely proud and glad that you realize what he's doing to you. I didn't until he had broken up with me and I regret so much. I thought it was my fault and I didn't say anything because I thought it was normal, that was how relationships were supposed to be.
With that done you need to just get out. He's not going to change for good, he just won't. It's not that he doesn't want to- he really may want to, he just doesn't know how.
YOU DO NOT INSPIRE THIS IN HIM. THIS IS NOT YOUR DOING.
The reason he acts like this is because it's all he knows. He doesn't know how to be loving and caring and understanding with out trying and focusing and really thinking about it. Why this is? I can't answer, but there are many reasons. But the important thing is that you know it's not you, and that you know you MUST get out, as soon as possible.
If you live with him, get a friend over and get help moving out. If you don't, and you're really afraid, bring a friend with you, meet him at a park or something, and break up with him. Somewhere that you have the space to tell him why and answer questions if you want to, but also where you can leave if things get bad, and where a friend can sit near by and watch, but not intrude unless necessary.
His next girlfriend? Probably not. I don't think mine changed for the next girl. And if he did it was only briefly because a matter of months later they were broken up and he was trash talking her.
I've always been one to think about the next girl. How will I compare? What stories will he tell? What things will he say about me? I hear all he says about his exes to me and it worries me how I will turn out in the final analysis when all is said and done. You can't think like that.
Be strong, break it off, just move on and don't look back, no matter what.