I did want to point out (I'm sure you noticed) your H's confusion around what time you were leaving. My W is the same. Times when she'll ask the same question multiple times. Or tell me one thing and then tell me something else, later.
I used to put it down as lying and deception. I have come to really believe it is that MLC confusion. Mind you, my W's could be due to medical conditions or medication... but it's only within the last couple years, so... perhaps that "fog" that is often referred to, regarding MLC.
So on that, I also think that you could do more reading on MLC, including going through some of the threads in the MLC forum here. There's a number of current ones that you may also find similarities with.
His POSSIBLE MLC should have no real bearing on you and your growth. Yes, it might be a catalyst for you moving forward for you. Still, you are moving forward... for you... with or without your H.
Regarding the D, it is what he SAYS he wants. Reality is, if he's MLC, then he likely has no idea what he wants. And putting that stuff about mediator on you? If he's MLC, he likely is unable to focus on doing the tasks he would need to do to accomplish the task, so he asks you to do it.
It is possible that, if he does not feel pressured by you, he will stop talking about D. Likely forget about it. But in the same token, he's not likely to start moving towards you, either.
He is on a journey that he needs to travel. The only way out of MLC is THROUGH it. That can happen with or without you in the picture. THAT is up to YOU. My sitch is one of those that got so far "gone", that it is best that I am mostly out of the picture, except with regards to the kids.
I also note that you mention your H being a dreamer and you being practical. Yet you later mention that your hopes and dreams of doing things as a couple have been dashed. I just thought that was interesting.
And with that also, I see you mention that you want to do things as a couple, without his friends being a major factor in it. I too had that desire. I get that. Whether he knows it or not, understand that is YOUR issue. It will be up to you to stop allowing that to hurt you. However that might look, for you.
Finally, just a thought about the bike and the plane. I'm guessing your H has his bike and pilot licenses. And you mentioned wanting to do those things as a couple, yet it hasn't happened. Does he fly without you? He obviously bikes without you.
You mention you thought those things were to be for the both of you (ie. at the same time), yet they are not.
So my question really is... do YOU have your bike and pilots licenses? If so, what's stopping YOU from going for a ride on the bike or taking the plane out? If you do not have your licenses, what's stopping you from getting them so that YOU CAN enjoy those two assets... FOR YOU?