Hello, this is my first time posting so if I categorized this post improperly I apologize.

I have 2002 Acura TL 3.2L w/ 265k miles on it. I love it to bits.
About a year ago I got 2 O2 sensor codes as well as a evap emissions code for my fuel tank pressure sensor.
I replaced both O2 sensors about a year ago with NGKs, and the upstream code went away, but the rear code remained.
I sort of ignored it for awhile because I really doubted the new rear o2 sensor was faulty.
About a month ago I had a sudden massive reduction in power, turns out the catalytic converter had mechanically failed, it was literally rattling around inside of itself and was preventing the engine from getting exhaust out, and thus air in. I just replaced it, along with a new denso o2 sensor, hoping that it would resolve the issue, but no
I still have code P0138.
I also did a bunch of other service along side the new cat, I adjusted the valves, I did new plugs, new valve cover gasket, intake and plenum gaskets, throttle body gasket and cleaned the crap out of everything with so much brake clean I was seeing a new universe.
The car is running great, but I really am at a loss about what to do on the O2 sensor code. At this point I'm starting to think the ECU might need to be swapped. I did my best to trace the wiring harness back and didn't see any evidence of chewed or ratty wiring, nor did I see any corrosion on the connectors of the ecu.

As for the P0453 FTP sensor high input code, I replaced the vapor canister purge valve/solenoid, the fuel cap, as well as the fuel tank pressure sensor and the code still remains.
Any suggestions would be greatly appreciated. Going to keep driving this thing till it falls apart, or I do.