I don't really have an answer, but I can definitely relate. DH and I have one DS who is almost 5. DH hasn't gotten the big V (yet), but he doesn't want more. I really feel like I want one more, but, like you, I don't want to force it on him. And if we did have another, I know I would spend the first couple years frustrated and resentful because of his lack of participation. DH doesn't have a lot of energy, and he is a major introvert, so he needs a lot of space and "decompression time" even with just the one kid, and he just does not do/handle the nighttime/sleep stuff at all. I'm 31, and although I'm okay with a larger age gap (obviously it would have to be at this point), I don't want the gap to be too huge, plus for health reasons (I have tested positive for blood clotting disorders) I don't want to wait much more than a year or two more. I really feel like there could be another child for us, and parenting has been so much more rewarding than I ever thought it could be... I just feel like I have so much to give another child. But I fear DH doesn't. So I am really at the same crossroads.
My plan has been not to talk about it for the past several months, just to kind of let it mellow, as the discussion really wasn't going anywhere. In the next few weeks, after I've gotten through some trips I'm taking for work and for fun, I plan to bring it up and say "let's figure this out." I would like us each to make a pros and cons list, and talk about it in a few pre-planned sessions. If we can't agree and/or it is painful or not constructive after a few conversations, I'll see if I can get him to see a counselor with me. He's not wanted to go to therapy in the past, but once he did mention he'd consider it for this specific situation.
All this to say I feel you, and to see if anyone else has any ideas!