Hmm. I think X is really very unsure of himself and never got out of his 20s in that respect. I think it is mostly about career and not feeling good about where he is in life, but not recognizing the link between actions he takes and where he winds up in life. You generally get out of things what you put into them, and often less. Marriage included, of course.
I think he is actually rather ashamed of OW but still fascinated by her, although I suspect that the fascination is now wearing thin. I hope he has the common sense to recognize that the odds are seriously against them if they get married. There are illnesses (mental and otherwise), huge age difference, starting of R in an affair, 2nd marriage, and kid involved--all some pretty serious roadblocks.
Not that that will stop the determined MLCer, but I hope X begins to see it for the childish antic that it has been, and OW for the user that she is. I actually feel somewhat sorry for her as she sees him as Daddy.
M: 16 years Bomb 4/07 OW 20s long gone Divorced 11/09 I remarried New Guy Cooperative r w/X regarding D