Missed your post but here's what I can say.
-Get good legal advice BEFORE you announce your plans to leave. Don't expect your Soon-to-be-Ex to be "nice" about this. Once you declare your plans to leave, it's an adversarial relationship.
-You have the right to stand on a moral code, aka, if he's doing something or engaging in something immoral, as well as illegal, you have every right to draw a line in the sand. I caution you about issuing an ultimatium however, because YOU must live with the outcome, not just him. So, if you're consequence is "stop doing this, or I'll leave," be ready to leave. He will either deny he's doing it, or he'll promise anything and keep doing it. Caveat: DO NOT be party to something illegal. You could get charged with being an accessory if you know but stay silent. When offenders are caught, they'll give up anyone and anything if they think it will help them get a lighter sentence. Don't be his fool.
-Be aware of those who counsel you "not to worry" if your husband "doesn't act" on immoral or illegal activity. Sooner or later, those who fantasize about doing something immoral or illegal, find an opportunity act out those fantasies, and that's when people get hurt. Don't be party to that by staying silent if you know something.
Is this easy? Nope. It's hard. That's the cost of having morals. It's the cost of doing what's right. I wouldn't wish the difficulties you face on anyone, but then, I couldn't live with myself if I had the opportunity to keep someone from getting hurt or from rescuing them from abuse if I spoke up. Find that courage. Someone's life may depend on it.
looks like the post was erased after it was written..
Anyway; well if you need to divorce then just do it but dont look back and have any regrets.. Sounds like you did all you could to stay in the marriage and left no stone unturned..
You just need to tell him you've changed your mind. That you were in shock and not thinking straight when he first devulged the truth to you, but now that you've fully absorbed the info you've realized you can't live with it. I'm thinking he's probably expecting you to ask for a divorce if what he told you is as bad as you say it is. Good Luck
So he has an illegal fettish, quite a few men do. Does he act on it?