I had to take a few days away from discussing this. I appreciate everyone's comments.
I cringe when I read implications that my husband has not been willing to make changes, and I cringe when I read implications that I have pushed him to accept my polyamory against his will. If anyone here were able to get to know us personally I think you would find two kind hearted and generous souls who are struggling to treat each other right. The poly-mono situation does not appear to have a simple fix, so it's not surprising that we have run up against challenges no matter how we've tried to resolve our differences.
What I have come to understand in these past few days is that my husband's biggest struggle in the one-night-a-month agreement has been the feeling he gets that he is providing a service (child care, running the household, caring for the pets, etc.) in order for me to go on a vacation to sleep with another man. The relationship itself is something he has mostly been able to tolerate for my sake, but his position of providing actual time and energy of his own in order to support it has been a thorn in his side. His past efforts to express this had not made sense to me, as it seemed like he was just complaining that spending time with our children was unpleasant for him, but now I understand what he is trying to convey. Tolerating my other relationship is one thing, but aiding it is another.
The trouble with taking away the overnight option is that we are back to the difficult situation we had in the past where C, who lives 5 hours away, can't make the trip just to take me out to lunch. He ends up trying to schedule time with me when he is on the way to or from other things. We had intended an overnight trip tomorrow, and I suggested that having had to cancel it, he would at least come to town for those two days and spend time with me during the day, but he has already reduced that to a 3 hour visit in the morning, since he couldn't justify giving up an evening event at home if we weren't going to be together in the evening anyway. I am back to feeling low on his priority list, trying to cram our time together into rushed visits, and not knowing when he might have time for me next.
Now my husband says maybe he's ok with the overnights if we aren't sexually intimate, which I suppose is theoretically possible. C says if he had to choose spooning over sex, he'd choose spooning anyway. Honestly the sexual heights he takes me to (even without PIV or oral sex) have always felt far too good to be true, so giving that up (for now anyway) is probably going to be ok. I'm wondering how to get sexually interested in my husband though. His desire for exclusive rights to my body flat out kills my libido. I'm polyamorous and celibate now -how's that for irony?
Married to a monogamous man 15 yrs, mother of 2, dating C 3 yrs, and in a romantic friendship with L more than 20 yrs