Digger,
Go ahead and start the bleach. You should take the chlorine level up to about 12 and try and keep it there. Test as many times a day as you can and each time, add enough bleach to get back to that level. Also, run the pump 24/7 while you are trying to clear this up. Backwash when your filter pressure rises 8-10 psi over clean filter pressure.

Your pH is a little low. Add about 1/3 of box of Borax slowly to the skimmer while the pump is running. See how much that raises it. You won't get an accurate pH reading when your chlorine is high. Test pH before adding doses of bleach. You are remembering correctly that muriatic acid is used to lower pH, something you don't need right now.

Don't worry about adding stabilizer (CYA) right now. Take care of clearing the pool first and add CYA later. Your test kit's reagents should still be fine as long as they were stored in the house over the winter.

You are remembering correctly that I am the one who has had cancer twice in the past 3 years. By the grace of God, I am currently in remission and praying to stay that way. Thanks for asking.