Hummmmm are you sure your husband has filed? I think there's some time limits on serving and responding although I'm not sure how that changes from state to state. I know I had 30 days to respond after being served.
Would you say your husband was in depression prior to the A? My guess is most people are really susceptible to wanting more of those feelings that the bio-chemical responses elicit during an affair. I also think living in a relatively permissive society doesn't help.
I'm sorry to hear about your husband living with OW and her family. That must be a cozy situation.... What is your home like at this time? Even though I've always been pretty neat and clean, when my husband left I worked even harder to make sure it was clean, comfortable, inviting, good scents, etc... (like a model home). I know that sounds a little overkill, but I felt that having a comfortable and inviting home helped make coming back look all the better. I'd also do things like make cookies (I do love baking!) and either give him a ziplock back with some or leave them for him. I'd make excuses for this like... "well I just happened to make some cookies and it's too much for just me and the kids so rather then let them sit and then have to throw them away... here's some extra for you."
There is no arriving, ever. It is all a continual becoming.