I don't think it has anything to do with the porn, it's an issue where he's not sexually attracted to his wife, at the moment..
Porn is simply an outlet to fill and provide enjoyment in something that you are not getting fulfilled in other areas.. There are times where we don't find out partners as attractive, or they are not able to meet our needs at a particular moment, or even a period of time..
From the perspective of a male, or at least me, I go through stages where certain types of sex really turn me on and it's something I can't get from my current partner.. The reason why could be a number of reasons.. Maybe you're embarrassed to ask, you don't want them to see you differently.. Maybe you don't trust them not to throw it in your face at a future time when you're in a fight..
I was watching alot of fisting videos recently, why, I don't know, it's just something that I found interesting at this stage.. I wasn't having sex with my husband and then I decided to play around with him one night and we gradually got to a point during sex where he fisted me.. I was really nervous and unsure what he would think of me if he knew I was interested in that, so I looked everywhere.
You have to ask, to communicate about the things that turn you on.. We are ALL sexually fluid.. One moment it's one thing, the next it's something else.. It's not easy to ask, to feel vulnerable to judgment, to risk making them feel worried that they can't fulfill your needs..
Porn is not the problem, it may be what's saving a relationship UNTIL YOU COMMUNICATE your needs.. If you don't, then porn is all you have and your partner will continue to not turn you on at that particular time..
Remember, we are all fluid.. Fisting is my thing right now, something else will eventually become my next new "thing..." and I need to communicate my needs to my partner..
It's not easy.. Good luck..
Ps. If you're finding you're attracted to the same sex, or opposite sex of your partner, then that's another big issue to work through..
But communicate with them, it's not easy.. Good luck..