I have to give you support on this one, I had less boundaries but they were still deadset important (regarding rings, use of my bed, what's discussed) initially, some of those have laxed with discussion; but if I got resistance on any of them it would be a reg flag...from the sounds of it you are being reasonable with your boundaries, if he has issues then you and he (and the third) need to reevaluate the situation.
Initially I did what I was comfortable with, set boundaries to my comfort level; I didn't worry (at least not that much) about TP and Mr. A's relationship development....and you shouldn't worry about his, do what you need to do to be comfortable, happy, and functional in your life. If he can't tolerate that then you need to figure out a way to discuss issues that doesn't become a wildfire.
Polyamory is wrong! It's Multiamory or Polyphilia. Mixing Greek and Latin roots? That's wrong.