Low pH is a priority but actually, you can work on both of those at the same time. Add a couple of cups of Borax slowly to the skimmer while the pump is running. Then, add some baking soda. (It's ok to do so right after the Borax.) For every pound of baking soda you add, it should raise the alk by about 15ppm. Aim for 80-100ppm. You might want to add the baking soda in a couple of doses instead of trying to get there in one big dose. A couple hours after adding, retest and add more Borax if needed. You need to get it above 7.0 asap.

Don't worry about low CH. It is only a problem in a vinyl pool if it is high.