Yeah I can imagine it is shit for both of you, but you're not the one having to live a sexless marriage and being rejected all the time OP.
If you don't want to have sex with him that's absolutely fine. But you need to be honest and divorce so he can find somebody who does want to sleep with him.
Men aren't rocks. They have feelings as much as women and anyone who is constantly rejected by their partner will mentally suffer. His self esteem will hit rock bottom. He isn't stupid he probably knows that on the odd occasions you do have sex you're only doing it to get it over with.
I understand it's shit for you both but you're coming across as the victim here and making it all about you. Do you really think having a wank for the relief is the answer?? It's not just the physical aspect of sex he misses it's also the intimacy and everything that comes with it! And no, kissing is not the same.
I think you're being pretty selfish here OP. Yeah he may be adamant he doesn't want to split but he will want to eventually. You're forcing him into a life of no sex and constant rejection from the 1 person who's meant to be the opposite towards him. That's gunna do some confidence damage to anybody.
Do the right thing. Either sort out your sex life and marriage or let him go to find somebody who wants what he wants.
If my partner had your attitude I would've walked a long time ago. You're lucky he's been so patient.