eggplanty, if you don't make him go and at the very minimum have a separation with counselling what will happen is that he will be good for a little while, then it will start back up again, and the next time, you won't fight so hard - and eventually you'll wake up, old, wondering where your life went.
I hate saying that, I am so sorry to say that because I know what it is like to love someone and have a situation you can't imagine leaving but if you don't show him that you are serious, that his behavior has the REAL consequence of losing you and his children - he won't ever learn.
I think he needs individual counselling to figure out quite why he feels the need to watch strangers strip on the internet. Despite how "oka" society is becoming with this behavior...it's actually not normal.
Moreover, your husband is actually supposed to be the one person in the world you can completely trust. With that gone now, he has to do the hard work to earn it back again.
My heart breaks for you because I have been there, and it is so hard to believe it and so hard to look at the face telling you that he loves you and is sorry and not want to believe it - but just try and put yourself in his shoes.
Could you have done that? Stripped and masturbated yourself for men on the internet while he was at home with the kids, in bed, at work or wherever and then come to bed afterwards and acted normal as if nothing had happened? It takes such a massive level of deception and such an astonishing lack of morals. It's hard to really see how bad it is at first (the shock takes over) but once you meet and talk to "normal" men you sort of realise most guys don't do that. Not even the single ones.
if he can lie about that and sleep at night and play the role of Mr Perfect Husband, ask yourself what happens when you are older and there's a cute young new receptionist at work. Do you think he will think twice about shagging her? Because he won't. These men have a sense of entitlement to get there kicks however they want and they will say (and even actually believe it themselves) that they "love" their wife (mine still insists he loved me desperately) BUT that just.is.not.LOVE.
Love is honest, love is truthful, love is loyal, love would never hurt or disrespect or dishonour or betray.
Some people, not just men, have this uncanny ability to compartmentalise. They put their Good side on display and do questionable things and in their minds they have a dark compartment for that stuff and they believe one has no bearing over the other.
My ex's wife before me did not like sex, was not into it, was not well groomed and she was unaffectionate. He did all the same things with her, and then when he was with me even though I was the opposite of that he did all the same things because that was just WHO HE WAS and it would have not matterred if he had been married to Angelina Jolie with nymphomania. He still would have done it.
If your DH has any chance at all of being the man you deserve, he should go into counselling, and he should learn about values, about integrity, about communication, about objectifying women for sex instead of getting his kicks form his loving partner and he should reform himself. I don't think anyone is beyond hope - but all the while it sounds like he is either trying to blame you or come up with other reasons why what he did was not that bad - he is totally unwilling to accept either responsibility or guilt.
Bad sign! Just wait till a man like that meets someone else....he will be out the door so fast your head will spin because it is all about him and what he needs.