From what you just said about the holiday incident 25 years ago, your Mother has always been selfish, now she is older and selfish. Being a parent, being an older person does not give your rights over your family. Try cutting down a bit at a time perhaps; maybe cut your calls (what on earth do you find to talk about?) to twice a day from three times, then cut it to one. You cannot possibly ignore your own time, needs, wants, and that of your own family, so maybe gradually cut your visits? You Mother has plenty of companionship, more than many of her generation do. Your brother sounds like an enabler with his comments about her being able to cook and look after herself in her early 70s, most of us do, unless we have some sort of physical difficulty.
But, if nothing else, come on here for a vent!