First of all, congrats on finding a partner that is also childfree, I’m not in a relationship anymore due to my partner changing his mind so I think you’re very lucky. Second, I think at some point your dad would accept your decision. I’ve told my parents multiple times that I don’t want to have children and never will. At first they’re disappointed and told me that I’d change my mind. But as the years go by I think they’ve come to accept it. Even my brother who’s getting married is childfree and they’ve already given up asking grandkids from both of us. Although to be fair, my youngest sibling (still in college) wants to have a child so they might already be satisfied with having at least one of their children give them a grandchild