You want the SPD at the panel on its own separate breakers. So, unless you plan to put a sub-panel out by the equipment pad, I would just install the SPD at the panel. It will still work and protect your pump. I’d get the HEPD80.
As for the Polaris line...can you convert it to another return? Depends on the line diameter I suppose. Some people recommission them as a water feature port for DIY fountain coolers.
Leaky/blocked bubblers....what about putting a DrainKing in the line at the pad and seeing if you can force water out of it using a garden hose? Otherwise it’s digging up lines and jackhammering the deck to get at the pool connections