"When he’s upset he won’t talk to me at all, and I always give him time but nothing is ever solved because he avoids talking about it ever. He refuses to go to therapy with me, dismissing it as “rubbish anyone could do” and calling me foolish just for suggesting it."

I've got to say, I take that as a major red flag, right there. Therapy is not "rubbish anyone could do," or else it wouldn't exist as a business, would it? And him calling you foolish for making the suggestion.... that would make me very nervous, if it were my fiancé saying such things.

Plus, problems need to be talked out. Unwillingness to do so is another warning signal.

Anything that annoys you a little, now, will drive you stark raving bananas once you're married. Please proceed with caution. If you go through with marriage, with these problems in place, things will only get more difficult.