I'm quite surprised at the reaction here, TBH. I think it is very normal for men (and women!) to look at porn, whether they are in a relationship or not. If there is not much sex going on between you (which is understandable given your circumstances) then he is obviously feeling frustrated (but Im not trying to place the blame at your door here, just looking at the facts) and finding other ways to get his kicks. Thank goodness he is using porn to do this and not actually shagging other women!
My OH likes a bit of porn now and then. If it involved animals or other weirdness then I'd be worried but it's just normal, run-of-the-mill stuff. He uses it more when we are having a 'dry patch' and I understand that. He uses it privately, in his own time, it doesn't interfere with his work or his relationships with me or the children, it has not 'escalated' in the 10 years we've been together.
I do have some reservations about porn re. women being exploited but a) that is not always the case and b) it is not my OH's fault! I wouldn't dream of telling my OH not to look at porn; he is a grown man and can make his own decisions. I don't control what he does.
Having said that, I wouldn't be happy about dating sites and would initiate more discussions about that.
I'm really surprised at the number of posters advising the OP to leave her OH! What about a bit more dialogue, some counselling etc? OP...I do understand how lack of sex can create tension between a couple, OH and I have been there many, many times. Sometimes it's me that doesn't want to, sometimes it's him. We try to keep communicating and that really helps.
Hope you can find a way through this.