The age gap, I can't really comment on; all bar one of my experiences with relationships were when I was in my early twenties, and went so dismally that I just gave up and assumed that I'm simply not relationship material. The only relationship I've had since was for a month or two well into my forties; there was quite an age gap, but in the other direction. I still don't quite know why that relationship ended (amicably). She seemed very concerned that she wasn't meeting my needs (she was) as much as that I wasn't meeting hers (don't really know, maybe she was trying to let me down gently.) In the interests of remaining friends, I didn't want to push for a detailed critique, but I have no regrets or hard feelings, though I am still very perplexed by it all!
I was very conscious of the difficulty I was having expressing my emotions, and this always makes me extremely anxious because I know that not being able to say how I feel can very easily be misinterpreted. Given her concern about her not meeting my needs, I must not have been expressing how much she meant to me anything like well enough. I have the trait called "alexithymia", which makes emotional processing very hard for me; I have them, but can't identify them very well. Probably less likely in your case, as you say that you are connecting emotionally when you are together.
As far as just his age is concerned, I think that may be a factor. Certainly for me, at this age I'm very well settled into the adaptions that I've made so that I can live out in a mostly non-autistic world. Doing things in a fairly rigid, routine way, almost on "auto-pilot" sometimes, is one of the ways that autistic people cope without overloading their brain with decisions to make and new things to learn. After decades of honing my lifestyle to best suit my autistic traits as a single guy, my habits are extremely ingrained, and changing them can feel like I'm throwing away my whole life support system. My ex has a very different lifestyle to the one that I'm used to - she is very gregarious, and unlike me has children and grandchildren. We couldn't really share each other's worlds enough because they were just too different, and although I would have loved to have immersed myself in her world more, I didn't have the adaptability to really make it work.
That (possible) lack of adaptability is what I was getting at in the post about not being able to influence the "switch". As BeaArthur said in her post, don't expect to change him. That's good advice with any partner, but change can be a particular difficulty for autistic people, and maybe more so if we have spent decades honing our survival skills.
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When you are fighting an invisible monster, first throw a bucket of paint over it.