Thanks for sharing this!
It is challenging! So far what's worked for me in the limited dating I've done in sobriety is dating another single parent and we all go out together. I guess if they run it's a good indication that it'll never work out in the long run. Yep, privacy and intimacy come much more slowly, but for some reason it feels good to test the waters and find out how we all work together.
As far as what happens when they're with my ex, I try to accept that I have zero control over that. I do my best to keep my side of the street clean and do the right thing, and in return my children and I have learned a fairly mutual amount of respect for each other, and we share a lot of love. I'm still working on being a disciplinarian, always wanting to be the "nice guy" to my kids, and looking for a good balance somewhere in between;-)