8 Years with my intergenerational SO (30/47) and our sex life has completely vanished. Advice?

So is 47, I'm 30. We've been together for 8 years. He refuses to discuss it, and sees me as being petty and immature for constantly bringing it up. I don’t know what I’ve done or haven’t done, and it feels so incredibly awful. He has flat out said that he won't be in an open relationship. His view is if it came to that then "what's the point". I feel like I'm being forced into abstinence against my will. He hasn’t made love to me alone at all in over a year. The only exception is once a few months ago when he begrudgingly let me give him a BJ then jacked me off with a grimace and said "just hurry up and get this over with." Exact words. We've tried having threesomes, since we have in the past with no issues. The handful of times we’ve had sex it’s been because he brought another guy over, who is without a doubt, every time younger and smaller than me. Clearly his type, not mine. It honestly never bothered me having a guest in bed before, I enjoyed it too, but it does now that this is the only way I've been able to have any intimacy with him. He picks up these boys off of grindr and I see him with it open all the time when I'm talking to him, but the last time he saw me laughing while joking with someone on grindr he got all jealous and flipped out. I’m petrified that he's no longer interested in me because I’ve aged out of his taste in guys. When asked if that's the case his answer is that I'm being paranoid and he uses the line "why would I trade in a ferrari for a toyota?" We've had a months long dry spell before, then it came back again, but this time it feels very different and it's becoming an all consuming thought.Any other long term gay couples with this problem? Any intergenerational couples? How did you handle it? Everything else in the relationship is pretty damn good except for this. I'd feel like I was being petty to leave over it, but I can't be faithful for this long without any intimacy. Eventually something's going to give.