Wow! I wonder how you got so many phosphates into your pool. If it didn't come from the initial fill which I presume was from your own water (was it?), then the only other source would be from some metal sequestrant products. Since you may have filled from well water that could have had metals, did someone add metal sequestrant to the water, perhaps on startup?
At any rate, you should probably use a phosphate remover to get the levels down, though that's usually the last thing we recommend since it's so expensive and usually isn't needed. But with 6000+ ppb phosphates, that just seems way too high. But wait a bit on that and keep reading because...
The Taylor K-1106 test refers to the following possible interferences with the test:
Silica, ferrous iron, fluoride, and sulfide may cause interference; to prevent, test for suspected interfering agent, dilute sample with DI water as necessary, and retest.
The only item that seems likely from the well water would be ferrous iron (though technically in the presence of chlorine in your pool it should have been converted to ferric iron). Have you had your well water tested for metals (typically iron and copper)? Maybe what you are seeing is just a high level of metals.
And maybe, keeping fingers crossed, the high phosphates or high metals are causing a false reading for Combined Chlorine though that isn't mentioned in the possible interferences in the FAS-DPD chlorine test.
Richard