Forget about what he is doing. He's the one that's missing out. Your son, to a degree, but in my opinion it might be better that he is being raised by a great mom, and being shown how to live an honorable life, rather than getting overexposed to a cheating jerk, who would tell him what he is doing is alright. Your son not seeing a lot of your H might not be a bad thing, is all I'm saying.
There are better male role models in the world. Coaches, teachers, friends... they don't even have to be "significant others" to you to be examples in your son's life.
