Beelzy

Did the water level drop to where the pool light is?? Could be a light niche leak at the area where the conduit is connected.

The guy is ripping you off! They only run around 1k......as most other salt units. Google is your friend.

Generally, if a motor trips the breaker and hums when turned back on, it's a short in the winding. Caps do go bad, but rarely trip the circuit breaker at the same time.

You don't need the spring assy to work the clamp. A BRASS nut and washer will work just fine. Make sure it's brass or the next time you strip something it will be the bolts on the clamp as well as the nuts.

The Polaris ATV's don't waste the gear boxes near as bad as when they first came out. I know a couple of chaps who have them and really like them a lot more than the Hayward Navigators they used to own.

Dude! Your pump is so in-efficient that replacing the whole pump complete, even to a single speed will save you $$ (You will probably be able to get by with a 1hp unit too)

The new Pentair lights are flawed by design, and should be replaced as a unit when the bulbs go bad. For the record, I have seen Brand New Pentair lights with fouled up lens gaskets, so even they can't do it right.

Keep up with the chlorine until you get a new filter cartridge. The degrading one is putting fine particles back into the spa and is causing the excessive sanitizer consumption. IMO

Check into the Nature2 ionization system. No electricity, easy to install and maintain. I had one on a aboveground pool for a while and the Nature2 killed the case of Athlete's Foot I had.....seriously!

They are running the chlorine exceedingly high.....probably had a Rhino-virus outbreak recently and are over correcting. What is with that CyA reading of 3.0?? Must be 30ppm is would guess.

Check the Alkalinity of the water. if it's too high 100+ the salt cell will produce white-ish looking deposits through the return line. If the debris really is "sand" and it's always in one corner of the pool, then a return line is cracked and bringing the sand into the pool. Good Luck!