It is very typical for someone with unmanaged PTSD to self-medicate with alcohol, drugs and so on. It is not wise to do so, however it is common. Hurting the ones you love the most is true in any illness, PTSD included, as those are the people you trust and feel most comfortable with. In general, even without an illness, people tend to take their frustrations out on those closest to them.

I suppose I should have said also in Jim's case, he did not have a girlfriend or mistress, he had been cheating on me with several prostitutes. He did not have an emotional attachment to any of the women he was sleeping with, so I believe that helped me to accept the situation more easily. If he had a mistress or was living with another woman unbeknownst to me I am uncertain how I would have felt.

It is far too soon for you to even consider a future with him, please don't try to think about it right now. Jim and I were separated for several months before I even considered taking him back. Right now you just need to take good care of yourself and your girls, feel angry and grieve for the situation as need be.