Some boyfriend. You can't let his pitiful life result in a pitiful life for you.
If you dream is to go to a special school, wherever it is, then do everything you can to go there. If your bf leaves you, it doesn't sound like you will be the worse off for it. In fact, he is probably aware that you will find someone better than him - someone who will love you and respect and not "lay down the law" when it comes to doing something to better your future.
Only you know your financial situation and what you and your folks can afford. If you can work it out, and it is want you want, then go make it happen. But, look at your Mom's viewpoint - it may cost her a lot of money and if you can get just as good of an education in-state, then staying put might be the wisest thing to do.
If your bf tries to kill himself of whatever, realize that it is not your fault! If you stay with him, realize that he will continue to threaten you with this and hold you captive. Tell him to go get help, and you get on with your life.