To your question when is enough enough? I struggled with that myself. I always wondered at what point to I go from "hero" for standing up for my marriage to doormat.
That day came 3 weeks ago for me. I had such clarity that enough was enough. She served me the D papers and although I could continue to stand up for my marriage, I suddenly found it incredibly easy to sit down. You have been at this 16 months. I have been at it 11 now. My wife has been out of the house for 8 months, so that makes it a little differant.
IMHO, continue to DB and PMA, for Mark. When the time is right you will know it.
Me: 44 S: 17 and 7 Final-6-13-08 I once went to a psychic who told me I would soon feel cheated......