I know it's controversial, but what motivation to you have disclosing the affair? My thought is that there was a lot of lying inside an alcoholic, broken marriage, and considering it's done and over, there's no catalyst to confess it. If down the road the subject came up organically, I would consider discussing it. Until then, it just seems as if you'd unburden your conscience at the expense of everything you profess to work towards.
Focus on yourself and your life. Why did you end up here? What is in you that draws you to unavailable men? What do you need to feel good in your life with your decisions? These are the things I'd be working on if I were you, and my boundaries would revolve around this.