Short version: How do people in ENM relationships with a primary romantic partner casual sex partners handle the question of frequency, how time is spent, what to do if the primary is starting to feel a lack of attention, etc.?

Long version: I'm new to all of this, please excuse and correct me if I'm failing at proper terminology, etc.

I had some more casual ENM relationships—both partners were NM—in my irreligious twenties, then spent almost fifteen years monogamous after a religious conversion. Now I'm back to my old self, and in a loving ENM relationship that's starting to blossom. The difference between now and my twenties is that I'm monogamous to him, but he is interested in casual kink hookups with others. We also plan to play together, though haven't found the right fit yet. I've searched my heart and this makes me happy and excited, and is part of a D/s dynamic that I'm very happy and secure with. I care most about being treated well, and he treats me like gold.

The boundaries and commitments right now, that he offered first, are that I am his primary and the only recipient of his love, the only one who comes to his home where I leave a lot of my own possessions, and other related things; his dates are just for sex. My boundaries are that I want it to stay that way—I don't mind sharing him sexually, but I am not able to share his love—and don't want any details of his dates, and I don't want to play together with anyone he sees alone. (Plus clean bills of health and all that). I spend every night at his house when his kids aren't there (50% of nights). He does not use our time together to go on dates, and based on his reports about evening kid activities, he's not going on very many dates, but there are some, I think (again, I don't know for sure, because I've asked not to know). My guess is that it would probably be about on or two dates a month for him. He also texts frequently and lovingly during our time apart, which is important to me.

I like the current arrangement, frequency, etc. It feels right. I feel as if I'm getting enough interaction, support, affection, etc. to meet that "being treated well" standard that makes ENM (or any relationship) possible for me. I have a fear that something is going to shift—maybe just the first flush of romance wearing off, which happens even in great relationships—and his frequency of dates is going to increase, along with time spent pursuing those dates on apps and at meetups. Since time is a limited resource, I fear that I'd be able to feel the loss of time spent on me, and then the mood would all change and I would start to feel a new jealousy that I really don't feel right now.

I know I need to talk to him about this honestly, but I wanted to do some research as well. How do people in this sort of situation handle the issue? Thank you!