I've been thinking about this thread all day and hoping the OP is okay.
It's made me think again about the power of porn. I remember when my son was about 11 and coming home from school on his own - the search history was there for all to see - boobs.com, breasts.com, girls.com etc.
I went onto one of the sites he'd been on and there were links there to sites which had pictures of sex with animals.
When I was young, boys had to make do with women in their underwear in Littlewoods catalogues. If they had a magazine, they were very lucky and chances are the images would be pretty tame by today's standards.
If 11 year old boys are accessing extreme pictures and videos at a time when they are really, really unable to cope with them, at a point where their hormones are rampaging through their bodies, then it's inevitable those are the things that will turn them on. It doesn't bear thinking about, that young men, who typically were turned on by just about anything, could only be turned on by extreme images.
I'm sure the OP's husband didn't start off with rape fantasies. They would have been apparent long before she married him. But by accessing porn sites constantly, I think he'd need stronger and stronger images to get turned on. Eventually she can't do it for him and the wanker's grip means that sex itself is often dissatisfying. So eventually he's found himself on rape sites - maybe ten years ago he'd be horrified to think he'd do that. Maybe even today he doesn't let himself think about it - after all, he might reason, she's asleep, isn't she? Why would she mind?
But now he's in a position where he doesn't want to make love to her. He doesn't want affection. He doesn't even want a blow job. He wants to reenact those films he's seen, that turned him on after he'd got bored with regular porn.
I don't think there's any way back, for him. He'd have to want to change, but whilst the siren of the porn videos is beckoning him on his computer and on his phone, I think it'll be impossible for him to resist.
As for you, OP, I hope you find the strength to get away from him. You can't be part of his cure. He's done untold damage. He needs intensive psychiatric help now and I doubt he'll go looking for it.