"I understand the need for perfection, especially from people you are paying to perform, but I would expect a modicum of acceptancce and understanding for those lesser mortals, like me, who mess up every now and then and need to read the words"
I am afraid you do not understand,performance is not about perfection, it is about learning how to cope calmly with your mistakes. Everyone can occasionally forget the words including Elvis Presley, THAT IS PART AND PARCEL OF PERFORMING.
How you deal with it, is part of performance, if you mess up now and again, you do not need to read the words, what you do is ad lib, or go to the next verse or sing a chorus.
what you suggest, is akin to riding a bicycle and when you fall off you go back to riding with stabilisers, well that way you never learn to ride a bike without stabilisers, you carry on like that you will never get the confidence to sing without words.
it is possible to sing well with words,but few people do, if people practised their songs with words they might be better at performing, they MIGHT look at the audience, TRAINED ACTORS can perform well with a word sheet, why, because they feckin well practice, they make contact with the audience, but far too often it is an excuse for amatuerism, unpreparedness, and fumbling paper shuffling, and poor performance.
liberate yourself throw away words, if you make a mistake learn to deal with it,carry on , or make a joke or sing the chorus or the next verse.
if this is any consolation here is Elvis, this might give you confidence not to worry about mistakeshttps://www.youtube.com/watch?v=dSeTA3549So