H said our M is "platonic"

[Crazy Eddie]

Once he said that he didn't have any intention of having a real sexual relationship with you, he lost all right to hold you to a promise of not having sex elsewhere. If you start dating and he complains, you can say "I wish things were 'different' but I'm content with the way things are now".

Or, to put it another way "In the near future, I will be getting laid regularly. Would you like to participate?"

If I am brutally honest, my choices are stay in the M and have A's to avoid completely dying inside, or getting out of this M and forcing everyone to adjust but hopefully all coming out happier in the end.
I don't want to do option 1. Too icky and it doesn't meet my goal which is to find a R/M that combines both love and sex. I just couldn't do that to H either. I love him as a person and don't want to be a jerk.

As opposed to him, who loves you as a person and is totally not being a jerk by insisting that you spend the rest of your life not having regular sex at all with anyone. It was bad enough when we were forced to live that way through several long dreary years of adolescence... this is the rest of your life we're talking about.

I'm not saying go to war with him or anything, mind you.

Last night he also said that seeing other people was a "dealbreaker."

You might want to mention that leaving you sexually frustrated with no intention to do anything to fix that combined with a demand not to get it elsewhere is also a "dealbreaker".

I guess that doesn't even make us best friends. It makes us cordial friends who don't even tell each other the truth.

You got it. He could use a good dose of the truth. If you're lucky, it might even get him to cut the BS and face whatever's going on with him and act like a real friend and maybe a even a lover sooner rather than later. But don't wait around hoping for it without really seeing it!