I am so sorry you are going through this. At times of great illness and stress people sometimes show can you who they are when you are least equipped to deal with it. It is one those awful ironies, at the greatest need that some people will choose that moment not to step up.
I don't know how you will ever get past it - I couldn't. For now we won't need to worry about the future or the divorce. The focus needs to be firmly on how you get through this, nothing else matters.
Can dd go and stay with friends for a few days? Please ring round and make arrangements for her. You do not need to be worried about her care as well at this time. Be honest and tell them the situation with your help and could they help for the odd night. Most people would gladly help. If this is not possible, how about family members? Failing all else you can pay for a babysitter to stay with her (and you)
When I heard surgery I hired some nurses this is possible to do through agencies if you call them. If you feel you can manage at home without one, then even a cleaning company can come over and help tidy the house, make you sandwich and do the household jobs.
You may need to throw some money at this, but I think you have to plan to not have your dh there.
Make plans for every part of your recovery - and tell him to go. There is no point waiting or expecting him to help, he has told you precisely where he stands - as painful as it is - you would be better to accept it, make arrangements, and when this is all over, I would ask him to leave for good. He did not have your back when you needed him most, he is no longer worthy of you or your life.To prioritise a walking holiday over you at this moment, with cancer is unforgivable.
Look after yourself op 