Wow, I am sorry that your dad was a walk away. If I knew that, I sure didn't remember.
Amazing how something that seems so simple, like checking a box on a form can be so fraught with complexity. Not long ago I had to fill out some sort of a form that asked my marital status and I wished that there had been a box marked "other" or a place to write a paragraph. I am not really single, but I don't really feel married, and in some ways I do feel like I widow. So instead I just checked "married" which is true legally, if in no other way.
My dad was also a walk away, but only for about 6 or 8 months around the time that I was 15. He had an OW, but I don't know if he lived with her or not, I rather think not. Wherever he lived (in some cheap apt I think) I never visited him there, but he did come to see my brother and I at the house.
While he was living (another 2 1/2 years or so) I never forgave him for it.
I think sometimes that part of the reason that I work so hard at this is because I don't want my kids to be left with the legacy of divorce and a walk away dad. I keep thinking that sometime he will return to his senses and become the man that I knew.