DS is 10 months, and his dad has shown very little interest since day 1. There have been 2 months without any contact, he never asks how he is, even when he went into hospital after breathing trouble for 2 days there was no reply and no asking how he was etc.
The lack of care reflects during contact, he will pay him little attention unless he is laughing/being very entertaining, will put him on the floor and sit nearby fiddling with a toy/his phone and occasionally looking at DS, and will call him stupid, weird and lazy regularly. He has seen him about once a week for the past 4 months, usually for 1-3 hours, but DS is in no way used to him. He cries when handed over usually, but is ok if put on the floor next to him.
Ex now wants to take him out on his own, he hasn't said where specifically, just out. The thing is I don't trust him to look after/comfort him at all, and DS would be completely confused and quite likely very upset, but equally I can't see ex improving and I can't say no forever. And it's not like a newborn where he is in danger of overheating easily etc.
What sort of age does it become unreasonable to stay supervising contact purely based on lack of care/attention to DS?