Here's the thing, you said "Get an f'ing divorce." to H... Meaning, HE should get a divorce. You said that he needs to leave. I agree with Snodderly, kml and others, he has to leave. You need to kick him out. But because YOU did not say that YOU were going to divorce, just that you were ready, NOT that you were going to file... you can take some time with that piece. After he is out.
You can take your time filing, if you choose. You have more pressing concerns than H and filing, imo, like S1, the baby, etc.
When W was flaunting her activities pre- and during anger stage, it wasn't as bad as you got...I never saw her and any OM together. So I havent had that experience. But if W were to do what H did, I would do as I advised you.
You know what's best for you. You have your family there for support, please involve them in helping you with the boys, the house and such. You don't need to fill them in with the gory details, you know that. You know they are there for you.
Hang in there your most awesomeness...
In the depths of winter, I finally learned that within me there lay an invincible summer. - Albert Camus
Uncertainty is the very condition which impels people to unfold their powers.-Eric Fromm