Get your degree and then dump him.
Okay, not really, but I'd have a serious chat with him. He is not your father and he is acting like he is. But, there may be a miscommunication. Maybe he thought you really wanted this and now he feels like you aren't trying hard enough to make up for his sacrifices. Maybe he does better with that kind of "encouragement" and doesn't realize it makes you want to throw in the towel.
He needs to accept that your feelings are valid. If you want to be an RN, find out how he can help, in a realistic and concrete way, and tell him. If you really don't, tell him that.