SD and Glimmer - phew! This is tough.
I too am coming up to the three year mark, and have a clinger, but not quite to the degree that you both have.
I did ask mine to leave 4.5mths post BD because it was seriously bad for my health and wellbeing. Actually, I said - you either need to get help or leave.
Of course he chose to leave and we didn't know where he was living for 3mths.
During this time, he came home every day, even if just for a few minutes.
At that point, I could no longer stand that, and took a couple of hours of arguing with him to get the information about where he was living out of him. He of course had run to the OW.
Knowing nothing about MLC at this point, I was so shocked, and asked him to hand back his house keys and told him he could no longer wander in and out at his leisure. He had to check with us first to see if it was convenient.
He used to spend all day Sunday with us, and pop in and out another couple of times a week (with permission), but has pretty much contacted me every day by phone, email or text apart from that.
Over time, I have gradually tightened things up and the time he spends here is lessening.
He has always spent the boys' birthdays, and Christmas with us.
He recently has half-heartedly approached a lawyer for a financial separation, and that provided the catalyst for telling him he was no longer welcome in the house while that was going on.
After a couple of weeks (and a big towards and then away from me), I increased that boundary to include, while he was also living life number two - he was not welcome to come inside.
He hates it. He is such a clinger. It is endlessly exhausting trying to keep him outside the building. It's often as ridiculous as a small puppy who is determined to get outside around your feet. He is the opposite - and is desperately trying to get inside around my physical body as a barrier. It is truly bizarre.
I have no great words of wisdom, just that you need to listen to your gut instinct and do what is right for you.
BTW, I do not regret allowing him in the house all of this time. He has been so 'out of it' at times, I did fear he might take his life if he didn't have access to me. I knew this being a process, me putting my foot down earlier wasn't going to hasten the journey he still had to take.
I didn't allow him to be here and monster at me either, so he has been reasonably easy to have around in terms of a MLCer (if that is possible).
In terms of them applying their feelings to you, I think that would have to do with their complete and utter self absorption. Depression is selfish. It's still all about them, so I would imagine that they think that everyone would share their thoughts and feelings, especially us.
A couple of weeks ago, I was having a long chat with my H, at his request, and in it he admitted that he and the OW had a tumultuous 'relationship'.
He said that she needed to get out of her previous relationship of 15 years (he admits he rescued her), because it was so bad. He said the guy used to be wonderful but developed PTSD because of what happened to him in his youth. (I have no idea whether this is true or not. This OW is definitely a BPD).
Then he said 'oh, he's a bit like me then'.
Do I think he thinks about what he has done to the boys and I? No I don't. It's all about him, and his need to rescue this wonderful person who needs his help.
The whole thing is very unbelievable.
It is tough making changes with a clinger. They will do some bizarre things to keep both worlds going - but I do believe if you can steel yourself to make those changes, they need to be made this far down the track.