I agree that unfortunately you can't force someone to change or accept that they need help - they have to come to that realization themselves. It sounds like you have done what you can to support him but he is not in a place where he is ready to accept help.

You might also be interested in information on Stages of Change. While originally created for alcoholism it does also fit most types of change/motivation. It can't tell you how to fix things but may give you an idea of where he is at. If he is willing to see a therapist that is a great start to allow him to discuss what he thinks the problems are (or aren't). Sometimes it is hard for people to hear their challenges from someone close to them but are more willing to explore it with a therapist.

It sounds like seeking out your own therapist is also a good idea and I would suggest having someone separate to the person he would see. It can give you an outlet as well and ensure you are able to take care of yourself.

I really hope it works out for you both