Oh dear x sorry for your dilemma.
Sounds very similar to my situation, which I'm gladly well over the other side now.
But 12 months ago, I could have mistaken your situation for my own.
DH lost interest.
Didn't have regular sex for years before we split up, but for some reason (I blame confidence on my part) I stuck by.
Just got from bad to worse to plane arkward and like you say, asking for sex is such a turn off!!
Problem was, I practically offering it on a plate and he would sooner watch porn; probably a questionable addiction. When confronted he would say "trying to get my mojo back". No matey, your suppressing your needs so you don't need to have sex with me!!
Needless to say, after 18 months at least of him giving me the brush off & at only 32/33 at the time I finally ended it & went back to my mums.
He never fought for me. Never questioned anything, from the day I left until the day receiving the equity release from our joint home was 28 weeks, during the midst of lockdown last year.
Truly one of the best thing ever did!
Used to be a bit of a drinker, but not near what your partner drinks