At one point, you need to make a decision. If he is causing too many problems in your thread, you should remove his ability to post in your thread. If it has gotten to the point that you are complaining about the person in Meta, it probably means he should not be posting in your thread. Otherwise you can remove his posts on an ad-hoc basis.
So far he is good. It seems he is calm but this taught a lesson. It's better if we have a clear direction from unofficial rules thread. The topic creator can apply a certain punishment if they are given the right.
But unless we have such direction, your proposal seems more logical however in the case of this particular user, banning him to post on the self moderated thread I have will open the door for him that he was thinking is close now. He will gladly use this opportunity of the exception 😉
I could give you hint on PM if you are interest or just leave it without bringing him here.