No ultimatum, until he starts getting nasty, and bringing up D talk again. You tried everything you knew to save your M, and that is so commendable. DBing says, though, that if something isn't working then try something else. Pointless doing the same thing over and over without results. I think if your H is in MLC then he will not heal or come back until he has 'crashed and burned' ---- he will have to go through the process. But, if this is just him spouting off, just bored and needing a 'something' different, then I say call his bluff. If he brings up D and leaving, walk to the door, open it and tell him he's welcome to use this facility anytime. You're done with this emotional blackmail so if he wants out then "get out now." This toughness could be a 180 for you since I think you are more the gentler kind of person who doesn't want to hurt his feelings. He may go or he may stay and work it out. But, how long can you last on this emotional rollercoaster? Whatever you're doing isn't working, it seems, so try something else. Oh, and definitely, cut off all wifely 'duties' --- if he doesn't even feel guilty about ML when he knows he's leaving (my H felt very guilty about this) then he has really detached himself from you. I'm sorry to say it, but I think he's just using your body until it's replaced with another one. This could also be another 180 for you.
Definitely, make plans for your future without him --- get excited about it. I did and I was almost sorry when my H begged me to come back. There's a big, wide world out there just waiting to be explored and not having to deal with your H's issues would be a huge burden off your shoulders. Perhaps you should go back to Colorado (I get the impression that's your home state) where you have family? (That's if you have to get another job.) If he wants you back then he's going to have to work for it, and that will mean he would have to live where you live, if it comes to that.
Feel the pain or not, but don't let him see that anything he says or does has any affect. Because then he controls you, and he knows it. He's using your pain to manipulate you into giving him what he wants. I am so glad that you haven't given in to signing the papers yet. You see! You can be tough.
As for friendship --- if they're in MLC, they won't care about your being their friend. Pointless even mentioning it. Half of what he says or you say will have been forgotten. My H said some really awful things that he has no memory of, and denies saying it, that, "I would never have said something like that to you." There you go --- how do you argue against that, 'eh? If he hits bottom, then he will come out and see if you're still there. If this is not MLC, then I think one has to wait awhile before mentioning your always being a friend, etc., at least until he has made up his mind what he's going to do and actually does it. Then, as a last resort, you can tell him 'the door may not be open, but I'll leave a crack in the window, but I don't know how long that window will remain open. I will, however, always care for you as a friend.' If you are still saying ILU --- stop!
If/when it comes to this point, I suggest you say as little as possible --- keep it as succinct as possible and firmly state your words so that he can have no question that you mean what you say.
Here is a statement you could follow if he starts up with the demands for D papers, etc., being mean, demanding, etc.:
Put your hand up like a policeman stopping a car, and say, "stop, enough, I will speak now." Point to the front door and say, "you are free, anytime, to walk right out that door. No-one is holding you back. I will take my time with D and will not be bullied into anything. I am done with this emotional blackmail and deem my wifely duties, therefore, are no longer required since you want to end the M. So, if you're not leaving immediately, then sleep in another bed, do your own laundry, make your own meals (and anything else you do for him). I will be moving on with my life and I know that no matter what, I will be okay. Do you understand what I am saying? (If he answers in the affirmative) Good, so I feel there is nothing more to discuss unless it's to say good-bye or you are willing to work on the M --- those are your two options right now, and I don't want to hear anything else coming out of your mouth." Turn around and walk away to your bedroom or somewhere private, and cry, breath, swear, punch the pillows (or all of the above). IMHO, it's time for you to take control of your life and this sitch. He's been pulling the strings for long enough.
Well, this is my opinion, anyway. Stay strong and remember that this too shall pass. I know how hard this will be. For instance, I could barely sleep when my H was in the other bedroom. I just wanted him to rush into mine and say that it was all a mistake, yadda yadda. You know, all that romantic stuff, but it didn't happen --- not for quite a long time. I sure cried a lot during those days. Everyone is different though, so you have to do what you are comfortable doing.
If nothing else, the message is --- do something different.
Take care.
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim