Every single day he's a different person and it's exhausting to know how high I need to make my walls that day. How long I need to keep the kids out of the house because I don't know where he is. If attempting to wait him out makes me seem like a doormat.
First off, I'm sorry that you are here. But you do have a great support system here so yes, do come here to vent!
I don't even know how you're doing it, because my sons are much younger and I already feel like it's sooo hard sometimes to keep up the front... yet your daughters are much older and I'm sure much more perceptive to the new dynamic in your M.
Keep your walls the same height. That's what detaching is all about, doesn't matter what kind of person he is today, you behave the same way. If he's being a good H and father today, be lovingly detached. If he's being an a**hole the next day, be lovingly detached. Aim at keeping your PMA everyday. Stay strong.