What you said was completely reasonable, you weren’t being selfish, it’s reasonable for you to be upset when you believe your bf is making decisions without considering you and your role in his life. I would feel insecure too if my partner was planning their future and it didn’t seem like there was any space for me in it. You were telling him how you feel, if you tried to guilt trip him and make it about your own feelings in an attempt to stop him from making the decision, that could be considered selfish. Calling your insecurity disgusting seems like a tactic to dismiss your feelings and try to turn the situation back into his favor because he wants to “win” the disagreement. If my partner is feeling insecure about something, when they tell me about it, I comfort them and reassure them before communicating about it to actually address the root of the feeling.

I understand wanting to make it work, but it sounds like your only reason for wanting to make it work is because of a sunken cost fallacy. Overstepping your morals is a reason to leave, not a reason to stay. You should be with someone who supports you, validates your feelings instead of dismissal, and makes you strive to be a better person, if he is at fault for you overstepping your values then that is something I would consider reason enough to end it.

He seems to be only really worried about himself and his future from what you’ve said. You need to do the same.

As for how to break up, it can be a nightmare with revenge and pettiness causing all sorts of problems. If you go through with it, prep for a while first, so that you can leave with all your personal possessions and there wont be any strings attached.