I think it’s perfectly fine to have boundaries but I do have one thing to raise.. you love your SO who is a father. So part of him and who he is is greatly defined by the fact he is a father. Part of a relationship is leaning on each other for support in many aspects of life. You don’t want to be a cook, a maid, a nanny, taxi or an entertainer to his kids which is a very large part of who he is. When he is struggling you don’t want to pick up the slack, you don’t want to be part of a huge part of him which I think could be very isolating. I think there is a difference between having boundaries about what you’re willing to take on versus wanting NOTHING to do with his kids. I would be sad to be with someone who felt like spending time with the people I love most was a chore. But again I think it’s very nuanced.