I am an alcoholic with 24 years sober. I say that to let you know that I have some knowledge of addiction and addicts. I hope what I have to say is helpful and know that it is meant in a loving and supportive way.
First things first, as we say in AA. As Hellfire said, he must be diagnosed by a certified CSAT. Cheaters can use the "sickness" of an addiction to get off of the hot seat. In reading your post, you describe a progression of increasingly risky, sexualized behavior, which means that compulsive thought processes may well be present - one of the symptoms of an addiction. It IS possible to self-diagnose as an addict, but the purpose of that is to begin the process of recovery, not as an excuse to rationalize dysfunctional behavior. The disease of addiction explains the behavior but it does not excuse it in any way. My advice would be to visit a CSAT for a diagnosis so that you can be sure of where you stand. It is very difficult to live with a newly recovering addict, especially one who has dual addictions.
My FWH is a sex addict. He was clean and sober from alcohol/drugs for 20 years. He stopped doing the things he needed to do to stay sober and to maintain a healthy spiritual condition: stopped going to 12-step meetings and stopped working a program. It took a few years, but he began an addictive relationship with pornography. I caught him a few times and finally began to see that it was becoming a problem for him and for our relationship. Since he had so many years clean and sober from substances, I felt that he could get the help he needed on his own. Sadly, I swept it under the rug and, like all addictions, it progressed into a physical affair. When my husband was caught, he was actively planning a second affair. Progression is the name of the game with sex addiction,
Sobriety from addiction is a LIFELONG process. If your husband is not actively working on the emotional and behavioral dysfunction that enables the disease, then it is almost a guaranteed path to relapse. He needs to learn the tools necessary to sustain long term sobriety and he can only truly learn those tools through work with sober addicts. In my experience, sustained sobriety is only possible with active participation in a 12-step program. Period. Not for a week, not a year, FOREVER. Sex addiction also requires individual therapy as it is a process addiction, which means it is a compulsion to continually engage in certain behaviors despite the negative impact on one’s life. Sex addiction, like eating addictions, are especially tricky since sex and eating are behaviors that humans engage in which are necessary for a healthy life. If you want a healthy relationship, then sex is usually part of that. If I, as an alcoholic, had to take a drink on a weekly basis in order to maintain a healthy relationship, then it would be extremely difficult to stay sober. This is why there is so much relapse for SAs.
TBH, an addict’s words are meaningless. Addicts are constitutionally incapable of honesty. ACTIONS will tell you if your husband is serious about being safe for you and for himself. If your husband will not do whatever it takes to get and stay clean, then he is not serious about recovery. I have been working with addicts for many years. They, like cheaters, follow certain patterns of behavior. They commonly promise a LOT of action while waiting for the commotion to die down so they can continue to use. Unless your husband actually follows through with his promises, then it is addict bullshit. Your husband has "used"/cheated before and still remained married. You are still married after discovery. Addicts can understand this as a "free pass", and will manipulate the situation so that they can continue to comfortably do what they want to do.
If your husband does not commit to the necessary work consistently and for the long term in order to make meaningful changes, you will be a hostage to his active addiction. As you know, life with an active addict is guaranteed to bring chaos and misery to your life. It is up to you to set the boundaries and expectations with what you can or cannot tolerate and to follow through with consequences. Addicts do not find sobriety until they hit their "bottom". If he is able to stay in the house and married to you without making any significant changes, why would he? He will not get better until he is ready and this is completely up to him.
This would be my list of non-negotiables:
1. 12-step meetings multiple times per week. They are online, so no excuses. He should start in AA since this is a much more stable program with a ton of history and people with long term sobriety.
2. Work with a sponsor. He will need to find one with some sober time.
3. Ongoing therapy with a CSAT. MC is not what he needs right now. The marriage is not the problem, HE is.
4. Taking the suggestions of his therapist and his sponsor and ACTING on those suggestions willingly.
5. Complete honesty at all times.
6. All electronics are open to your review whenever you need to see them and his whereabouts are verifiable. This is ACCOUNTABILITY. If he is misbehaving online, then I would consider computer use only when you are present when he is not at work.
I am an outspoken gal, and I will tell you that without honesty, there is no hope. If your husband does not get willing and honest at all times, he will almost certainly continue some sort of addictive behavior and you will bear the brunt of that. Addicts will take advantage of kindness, which they see as weakness, to manipulate in order to continue to do what they want. It is counterintuitive that kindness, mercy and compassion will enable an addict, but that is the truth of the disease.
You cannot control your husband’s actions or the outcome. He and only he can decide to get better. You need to take care of yourself first. If you have kids, they need to be far away from active addiction.