Sanderika (and all of the others who have contributed so thoughtfully), when my husband first filed nearly two years ago, I was in terrible pain. It felt like a complete rejection of the family and the marriage. He was then more than three years into full blown MLC - much longer in the mild depressive state that seems to be a trigger for so many.
The last two years have been a roller coaster in terms of our emotions and also our health. He can still turn on a dime. The difference between my h and so many others is that he cannot seem to have a friendship with me. He will rush back into my life like an express train and want to work on our relationship, for about three weeks, and then rush back into really mean spewing MLC behaviour. I am not so sure that the stages are altogethr helpful, certainly in my case . .
FWIW I do think that there are degrees of severity of MLC, I have known a number of men who have uncharacteristically had an affair, but chosen the family and put their marriage back together, even though it has taken time.
Then there are men who do seem to go through the stages, and have a 2-4 year full blown MLC [tough enough, but they seem to progress] I think these are the 'success' stories we see on this site. And then there are men like our husbands who remain unwilling to face their issues. Well educated, intelligent, and previously loving husbands and fathers, they appear able to abandon us long term. They don't seem to go through the 'stages' in any sequential way. I would say that my husband has been in all of the stages pretty much all of the time. I suspect that they may emerge periodically, realise what they have done and be so appalled they cannot do anything about it.
I think there may be a 4th group who are so damaged that they remain permanently in MLC separation without any inner knowledge.
One thing my husband said during a relatively recent emergence was that he thought by filing for divorce he could wipe the slate clean and we could start over again. They really are that confused. Their emotional landscape is almost wholly irrational.
As to your situation. You have managed to construct a friendship which I admire. As long as your primary motive is not punishment, in your shoes I would now gently withdraw the friendship.
You have nothing to lose. What you have done is good in that you maintained a relationsihp - something I have been unable to do. But now it is time for a change. You can say it or not. Withdrawing without explanation is more powerful in my view, because explaining implies that there is a relationship.
I think they decide on divorce for a variety of reasons, some of which are opaque even to them. If he thinks you are fine with his decision I think you may find that the NC puzzles him.
It is horrible - people in MLC are like full blown narcissists. They have no empathy and no compassion. Until and unless they come out of it there really isn't much we can do. You have done kind, and now perhaps you should withdraw for your sake.
Incidentally, and I hope this makes you smile, I was doing some work yesteday with a friend who has been with me throughout this horrible time. She said 'I do envy you your lovely single life' I nearly fell over. If they only knew the loneliness and anguish at times . . . . But it is good that at least I do not present as a terrible mess! And yes, a lot of healing has taken place. That is one of the advantages for us of NC - it gives us space to heal.