I'm going to follow up on some great points from Bigger...
I’m not so keen on people buying sex. If you have kids, then maybe try asking him if he would be OK with some random guy getting sexual service from your son/daughter – even if we assume they are 20 years old and paying their way through university that way. If we can’t accept it for ours – why expect others to be content with it?
Whoa, I completely missed the mention of prostitutes in your first post, OP. All affairs are bad, of course, but your husband's callous disregard for your health, squandering of marital funds for extramarital sex, and-- as Bigger put it-- purchasing the use of another person's body for sexual pleasure are indicative of a person who is missing an empathy chip. For this reason, I don't expect the "what if this was your son or daughter?!" argument to land with him.
Also, I'm willing to bet that if you stepped back and looked at your relationship with your husband objectively, you would observe that it's probably transactional in nature as well. Although he might not say so explicitly, he might feel entitled to do what he wants on the side because of whatever "services" he thinks he's providing you (for example, being the primary wage earner, or help around the house, etc.). You might also consider whether your husband actually sees you as a human being with your own agency and inner life or just as the "role of wife" that serves a particular purpose to him.
I’m a bit worried about your WH stance to IC. He seems happy to go to MC and all that, but the problem isn’t a lack of sex or not spending time together or anything like that. The issues are within HIM.
I differ from many people on SI in that I don't consider a WH's willingness or unwillingness to go to IC as a measure of their remorse or commitment to change, but I agree with Bigger that your husband's willingness to go to MC in lieu of IC is indicative of his belief that his cheating is a problem with the marriage and not with him.
But even if you do manage to convince him to go IC, keep the following in mind:
-There are limits to what IC can achieve. IC is not going to give your husband a character transplant or reincarnate him into someone else.
-IC is only as effective as the commitment and efforts of the person going into it.
-Therapists vary considerably in skill level and experience. Some can be manipulated easily by the clients. Most prefer a non-confrontational style and aren't going to call out your WH on his bullshit even if they detect it because they don't want to lose his business as a client.
-The IC's advice is going to be based on whatever your WH tells them, so if he's lying to, misrepresenting, or withholding information from the IC, he will (at best) get no benefit from the experience, or (at worst) he will get very counterproductive advice.
-Your WH might use his therapist as an excuse to do things you don't want him to do or avoid doing things you've asked him to do. For example, he might say, "My IC thinks taking a solo trip to Miami would be good for me!" or "My IC thinks you're being controlling by asking to read my emails."
-Even if your husband goes into therapy in good faith, gets a top-notch therapist, and puts in the work, your husband may, over the course of the process, conclude that the best course of action would be to get divorced. What's good for him as a person might not be what's good for your marriage.
And lastly, I think you would be best served by focusing less on him and what you can do for yourself. As a first step, you should cease MC and find yourself an IC instead.
[This message edited by BluerThanBlue at 6:07 PM, Wednesday, January 22nd]