I've been following since the original thread.
I'm sure that your parents don't feel that way about you, and no one thinks you are a shit wife or mother. You are under immense pressure and still breast feeding and taking care of your girls, doesn't that make you amazing? I think so.
Living in your parents' house under these circumstances is really stressful for you and them. You seem to muddle along with them in the lulls between the 'big reveals' from your H. When something big happens as the next stage of this situation/process you are in, it puts extra strain on you and them, and perhaps that is like the tipping point where you all cannot cope and thus have an explosive row.
I have the same happen to me as I, for totally different reasons, also live with my parents. It's very hard to be an individual adult making all one's own decisions in such an environment if you have difficult circumstances to deal with. Your parents trying to control things is perhaps their way of coping with the situation and also because they must feel protective of you. Not that this makes it any easier for you, but everyone flaring up and arguing during these moments is probably a natural consequence of the situation.
Now you are faced with these big decisions over your house, you can take some control by starting to dictate how you want this to go. I think when we are able to take control a little it also gives us some of our power back. That helps when we feel powerless and are falling apart.
I have a feeling that your H may seem to be having the easy life and to be happier because he is the one calling all the shots. Yet, surely a happy person would not be able to do this to their family, so his reality is probably quite different. Just because he got to run away doesn't mean he'll experience happiness, he just doesn't have the responsibility... That's not happiness though, I don't think. It's just existing. What does he actually have that is so great apart from not having to care for his children day to day? I would rather have a loving family like your family (I know you argued but that's temporary), two beautiful children and my integrity intact - that's what you have!
Not coping, not being able to make your own plans and relying on other people is not wrong... It's human.