Unfortunatly I've been down a lot of those cheeseless tunnels.
Christmas brought out a different side to my XH too. There was a lot of pleading and tears from him and he begged me not to walk away, but by the end of January, he had decided that he wanted to be with OW. They lasted exactly one week. I think if she hadn't gotten pregnant that week, he might have given things one more try, but that kind of sealed our fate.
I'm not sure if it had any effect on him or not, but my H started antidepressents in November, and then went off them in mid January. I don't think he liked facing the feelings he had underneath his depression. For him it was easier to go back to what "felt good," then to face the damage he had done. Your H's lack of contact may be caused by him not wanting to face his demons either. As long as he can keep at a distance, he can rewrite history any way he wants to, but one day he will have to face reality. Your MIL seems to be protecting him from this, but he can only hide for so long
