All of us at some point have probably wished that we could take our loved one back home as deep down none of us want them to need to be looked after however usually reality of their declining illness and complex practical needs kick in. It is tough enough for a daughter in my case for my dad but for a partner maybe other emotions are added factors. However it sounds as though much as your mum may not want to face it hence continuous moaning, your dads best interests are that care home is best from now on.
That's what is worrying me most , that CH is in dad's best interests but mum wants us to put her interests first not his.