You are so right that the codieness lingers ready to strike when we're not looking. I catch myself often, but at least, like you, I catch myself.
It's all your choice, but it seems to me that his owing you money gives him the power to make you happy or not happy, to make you work trying to get it especially when you have always been good at doing that.
I think I would either turn it over to a lawyer to pursue or just let it go and detach from the whole thing.
Hugs and thanks for the reminder to stay diligent in my recovery.