Kinder - Some of this may come across as a little harsh - I'm sorry in advance if that is the case.
You seem to be avoiding speaking to a lawyer. I'm not sure what the downside is to at least discussing this with someone (who could very likely give you a free consultation) and it feels like you might be afraid that this is a step leading to divorce, which I know you don't want. '
There could be a lot more to your situation than mere child support. For instance, you've been separated since May and it sounds like you've assumed more than half the financial responsibility for the kids. If that is the case - you meet the test to file as Head of Household come tax time. That could be a very meaningful financial move for you.
What concerns me in your situation is that you have a pregnant OW living with your H. I can tell you one thing a lawyer will say - and that is that when there is a third party involved advising the Walk Away Spouse, things tend to get uglier. They are going to look out for themselves.
Kinder - is it ok with you that your husband is living elsewhere and is having a child with another woman? It sort of sounds to me like you are giving your H that impression, given that your H feels comfortable voicing his concerns about OW's health to you and his complaints that you don't call him enough. If it's not ok with you then your behavior needs to be consistent with how you feel. You don't have to be hostile and can continue to be civil, but I would certainly, at a minimum, draw a boundary that you don't want to listen to his fears concerning the pregnancy.
