Unwell people can be manipulative too. Unwell people can be selfish too. Being unwell can make you selfish. There is nothing at all cruel or outlandish about that, it's intended as a reminder.
So again, the husband DID NOT KNOW she had cancer. Because OP DID NOT KNOW she had cancer at that point.
OP found this out later and has introduced it to the thread to try to make her case against her DH parenting his child more solid.
The husband has genuine reasons for concern that he will LOSE ACCESS to the child he fought so hard to see, and despite OP deciding his genuine concerns don't matter, they are still very much still his genuine concerns.
DH has been caregiing OP, taking her to regular hospital visits, and far as he knew this was just another medical incident in a long line which he has already been dealing with.
The only difference between this and all the other many hospital visits was that her daughter called an ambulance. Going to the hospital because she is sick is not an abnormal or unusual event. She has collapsed before too.
The phone call came from a girl who could not cope with getting in the ambulance and locked herself in her room rather than going to the hospital (no judgement on her, just stating facts). We do not know what she told him and we do not know how well DH can trust her judgement. We do know she doesn't cope with stress.
Stating these facts does not minimise OPs illness and is not cruel.
Her DH had, as every single caregiver has to, normalised her becoming ill. This is the only way to survive caregiving becoming your life - you have to be pragmatic about it.
Her DH WENT TO THE HOSPITAL, but he didn't drop something very important to him and go immediately, he went a few hours later.
OP is hurting nobody but herself by continuing this tirade against her husband. Let it go. Talk about what you want from him in future and also LISTEN TO HIM as he is not a paid nurse, he is allowed to live his life as best he can around your illness.
Sickness and in health does not mean "you will do as I say at all times drop anything I tell you to instantaneously and if you do not do this I will publicly slag you off and try to stonewall you back into compliance".
He is there in OPs sickness, he's just not an automaton with no right to care about anything else at all.
OP asked, people answered.
Wishing the OP good luck with her medical treatments, and good luck being able to absorb the reality that one thousand, one hundred and thirty online strangers have told her she is wrong.