Sounds like your R is making progress. There definitely is a balancing act that you need to do.
Here is my 2Cents (just thinking out loud):
So you want to back off some and add mystery. Lets start with the way you dress tonight. How would he expect you to dress? Can you dress different? (like you have a date??)
Don't linger around H tonight. If/when H approaches, be nice, then move to other parents and have "fun conversations". Laugh with them (You are fun to be around, others like being with you, they have no walls).
Be first to leave (you are excited about going out tonight).
"What is best for my kids is best for me" Amor Fati Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712