There is a lot of change and uncertainty in his life right now and that makes things worse. Once he figures out his income, living situation, and relationship with your daughters and isn't constantly worrying about it then he will stop lashing out.
It doesn't sound like he has always been this way, so I don't think it will last forever. Its fear that he is making a bad decision, fear of what people will think of him, fear that his thing with OW is not as great as he wants it to be and fear of all the change going on right now. The pace of change will slow but it will take time. In many ways he is like a cornered animal
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015