Welcome to the forum and I am very sorry for your situation. Now, it seems to me [I could have misunderstood you] that you have a misconception when it comes to parrots: they do NOT need any type of grit or grinding material in their crops. They are not like pigeons or any other species of bird that eats things whole and, as a matter of fact, giving parrots grit causes crop impaction so that would be the first thing I would look at in your case. Parrots 'peel' everything and grind it in their beaks before they swallow. Sand perches are a no-no for any bird [all they do is hurt their feet), If you are concerned about their claws becoming overgrown, I suggest you order some Sweetfeet perches. They have rough sides where the claws go but smooth and soft sides where the soles of their feet would go. They are also lightd and easy to wash - the only problem you are going to have is that the too will chew them up in no time at all
I have managed to keep a couple still in one piece after a few months with my too but he lives cage-free in a birdroom with lots of things to chew [branches, pieces of 2x4s, thick cardboard boxes, etc] - by the way, my female African Gray also gets along very well with the male cockatoo to the point that he actually strides her eggs in the nest he made for her when she gets up to eat during breeding season.
As to giving them an antifungal on your own... well, I don't know if I recommend that. For one thing, it might not be fungal. It could be a tumor, an impaction or, best case scenario, bacterial. Of course, you could medicate with both antibiotics and antifungals and hope for the best but, with sick older birds [and yes, at 33 years of age, both your birds are older because they simply do not live long in captivity], you need perfect husbandry, something you can no longer provide due to your medical conditions.
Now, I hope you don't take this the wrong way because it's not as if I do not feel for you or disregard your feelings for them or their feelings for you, but I love birds and I worry about all of them, not only my own and it seems to me that sooner or later, you are going to have to make a decision about the birds because, let's face it, time doesn't stop for any of us and, as we get older [and I am old myself, mind you] it becomes more and more difficult to fulfill their needs. I am moving back to my country where I have a nephew who loves birds and who has a son who doesn't only love birds, he is actually studying to be a vet and has already agreed to take my birds when I become too old to care for them properly. Do you have anybody who can come and help you with the birds? Things like disinfecting the cage and room where they are kept, take them to the vet for a proper diagnosis, etc. Because a swollen crop can be a very serious problem - and I am talking a matter of life and death...