Muriatic acid can be added slowly in front of a return jet, baking soda in the skimmer. CYA can either be added directly into the skimmer and then run the pump 24/7 for about 4 days while it dissolves in the filter. Or, you can put the cya in a sock and tie it in front of the return jet. Give it a squeeze a couple of times per day to help it dissolve faster. You do NOT want to add CYA granules in front of a return jet because since it is slow-dissolving, it will sink and sit on the pool floor for a few days. You don't want an acid sitting on the liner. You do NOT need calcium; you have a vinyl liner.

You have done the volume calculation correctly. I'm not sure about your question about turning off the salt cell during chemical applications. I'll let someone else answer that part.