Need advice on CEL P0420 and Air Fuel sensor 1 (AKA O2 sensor 1)

Been chasing that check engine light for about 6 months. CEL will reset if I pull off the negative battery terminal, but the CEL comes back after an hours driving at highway speeds. The latest test I did showed the data from sensor 2 downstream, but not sensor 1. Sensor 1 showed nothing (0.0 volts) from the OBD Link MX+ whether driving or sitting still. 275,000 miles.
Zero exhaust leaks. New downstream sensor 2 and new gasket installed last month. The two cats on this 3.4 liter V6 automatic are in series. Each one shows about a 100 degree difference from input to output after 10 minutes of 60 MPH driving. The engine timing is at 8 degrees BTDC with the jumper installed, but goes out of range when the jumper is removed. New timing belt installed 60 days ago. There is about zero carbon in the exhaust pipe and no odor or visible blue smoke. The compression is at 145 pounds all cylinders. I tested all the wiring from the computer back to the Air/Fuel ratio sensor 1 and got good continuity and B+ with the key ON. I ordered a new OEM sensor 89467-35060 today from Olathe Parts Online for 209.18. The engine still has plenty of power and I can run the A/C with no problems. Always starts easy, 21 MPG, not much rust (NOW), so overall a fairly good runner if not beautiful to look at. So I'm asking the forum members here-Please give me your opinions- Would you continue to replace parts until the CEL stays gone (new cats are next if the sensor 1 has no effect) I live in a state with no emissions testing, but I would still sleep better if I never saw that CEL come back on. Also- question- Am I going to do damage to the engine parts with the timing running off the charts? There is no knocking or running after you shut it off. If the CEL was disabled "for testing" would that obscure another fault that could show up later for some other reason? I also tested for vacuum leaks and nothing there either. Your help and advice is much appreciated! Thanks!