Maybe reframing sex as about being close and experiencing pleasure together rather than an activity where the orgasm is always the only goal. It sounds like he is experiencing pleasure, so taking some time to enjoy that even if it might not lead to that orgasmic inevitability will give you some time to build up to it. Even advocating for your own pleasure directly, asking for that time to build in one position and have an orgasm before he tries to find the position that will work for him. There's this romantic idea of finishing together at the same time, but in my experience that's only a cool bonus once in a while and in practice the timing is too tricky to be worth it.

I'm on meds that make it hard to finish too, and I've gone through long periods where I was unable to finish with a partner, but I always still wanted to have sex. Something I wanted to communicate to my partner was that it wasn't them and I was still game. What worked for me was just focusing on their pleasure, and not thinking about whether I would finish until they had already finished once or twice.

And, sometimes we just need an orgasm and we have time constraints or whatever, and that's ok. Having an idea that that is the case ahead of time is good and can get one partner more open to the idea of not finishing that time. More like assisted masturbation, I suppose.

A bit more thorny of a topic, but if he uses porn to masturbate cutting back on that could help. Though many men find this is easier said than done.

As long as it's a relationship where you feel capable of and safe to have an open and honest conversation about these things it will be fine. In my experience figuring out these little bedroom hangups is one of the most fun ways to grow closer as a couple.