It doesn't surprise me that your CYA is over 100--the trichlor pucks in the chlorinator are not only raising your CYA with each puck that you add, but also driving your pH downward. I strongly recommend that you stop using the pucks except in emergencies (vacations, etc) and switch to liquid chlorine, or bleach.

Also, with a CYA that high and keeping the chlorine at 4-5, you are walking a very fine line between a clear pool and algae problems. With a CYa at 100 or above, you should be keeping your Cl at 8-15 ppm at all times.

If you stop using the trichlor and aerate your water, the pH will probably rise on its own. If you plan to continue using the trichlor, I'd start with about 1/2 box of Borax and aim for somewhere in the 7.5-7.6 area for pH. It's always better to add a little at a time and "sneak up" on your target number, than to overshoot it and have to correct. Same goes for baking soda to raise the alk--it only needs to come up a little bit, so I'd start with a box and go from there.

Janet