He’s only been moved out two months. I would say that it’s not in the best interest of the child to meet a new partner for either parent yet. Young children will still be struggling with the separation. And wanting to settle and find their new consistency after a huge upheaval in their life.
he has plenty of days without the child, and should ideally use them for the new girlfriend.
could you agree a timeframe like 1 year, that would be more child focused?
You mention you are finding it difficult yourself and I would also seek Support for your own personal feelings as a separate issue. You deserve help too.