I cannot answer those concerns. I'm knowledgeable about anatomy and movement as it is the basis of my work, and I have taught it to people in my trade (massage therapy), both as a class and training a couple of apprentices. I have long had a bad injury to my knee, but recently it began to improve, and the PMR did not slow that process. As to the pneumonia, there is an ancillary condition that can result in that and you should perhaps be tested for it.
As a fellow 79 year old I sympathize with stubbornly doing things that are really not a good idea at my age. Working on that part! Finding a balance between what I can do and can't, and a need to retain whatever independence reasonably remains is tricky.