Eagle -- Don't label anything. Try not to notice what he is doing one way or the other. I know it's next to impossible, but try. You may have seen in my thread I thought I was "stirring the pot" and his MLC is now seven years and counting. And I have realized he may always have been mentally ill on top of that. Labeling will hobble you because it will give you expectations.
Don't make a boundary in order to affect his behavior or tell him what's what. It won't work.
Make a boundary because you need something. Do you need to not be around him when he is with the kids or are you willing to suffer a little because you think the kids like it? I am not saying it's good for the kids. Looking back, I think I should have kicked my H out long before I did. But if it is actually nice to be all together and he is not damaging them with his behavior and weirdness, then decide if you feel like being there or not and do what you want. Maybe some days you'll have plans. Maybe some days you'll feel like reading a book in the hammock while they are doing stuff in the garden. Maybe some days you'll leave for the weekend when he comes home. It's up to you, what you need to have peace. And you don't have to have a hard and fast rule if you don't need one yet.
I know a couple who has a relationship like brother and sister for many years. It's very sad on some levels but they are Catholic and very devoted to their kids and have made peace with chastity. I'm not saying that's a good solution, but just that you don't need a rule based on what the world expects for your sex life.
I believe I will see the bounty of the Lord in the land of the living. Wait for the Lord with courage. Be stouthearted, and wait for the Lord.