This is only my personal opinion and nothing more, so take it with a gain of dirt.
It sounds like you both are sexually abnormal! You with no sexual excitement or feeling and him with no clue if you are orgasming or even enjoying it. (mind you I said sexually abnormal, not you personally abnormal.)
However, you both have made it 25 years! Thats a lot longer than most will make it on this planet!
My recommendation at this point would be to just go with it and arrange a set of rules where you both can get some enjoyment and togetherness time.
Meaning, tell him if he will give you a foot rub/back rub or whatever it is you really enjoy most, then you will give him sexually whatever he enjoys most. That way you both are getting pleasured, are together when you do it and both come away happy.

I would make sure that if he agrees to do whatever, say a foot rub, that you get it first and not after sex. A man who knows he will get sex for X trade/reason will flap his arms and fly to the moon to cut a small slice of cheese for a grilled sandwich before sex whereas, after sex, he will offer to walk to the cupboard and offer you a stale cracker!

Best of luck to you.