Engine Problems

I've got an '06 3.5L 4x4 extended cab that I'm currently trying to get back to smooth sailing... Originally bought it misfiring at idle, P0303, P0420, and codes for the camshaft sensors (can't remember them now). Also started noticing a low oil light at idle after the engine was getting on the highway. Since then, I've replaced the front wheel hubs, all brake components, camshaft sensors, o2 sensors, all spark plugs, all ignition coils, oil pressure sensor, and water pump. Cleaned out the MAF sensor, put a new K&N air filter in the box. Done a couple flushes of the oil and coolant, haven't noticed any particular discolorations or unwanted sediments in either. Transmission has a little jump to it at shifts, but it's a 4L60... I'm not too surprised. Fluid looks great in it.

The only code that has not disappeared is the P0420 code, and the symptoms remaining are poor/slow acceleration, rough idle, and I've noticed that the coolant temperature raises at idle after driving, highest being at 210ish. The slow acceleration is accompanied by a bucking when throttle is applied at highway speeds, but not feeling like it's the transmission causing it. I've noticed oil deposits around the valve cover, however I'm not thinking that would result in any of the aforementioned issues, naturally a problem to be sure but not a cause. Popping the air intake box off, I found a severely rotted and oily PCV tube, replaced it. Noted oil deposits through the box as well. Went ahead and removed/cleaned the throttle body before reinstalling everything.
I took the truck to a shop to do a basic compression test, and they found all cylinders to be 180psi but one, being 178. Didn't request a leakdown test as I didn't realize the production PSI was 215... Woops. I don't think they knew either. Engine is at 205k miles currently, is that a normal degradation for that mileage?

I'm curious if anyone else has thoughts on if dumping more money into this engine is worth it, or just buy a new motor/truck. Looking at the symptoms and thinking the next options are going to be replacing the catalytic converters and fan clutch, but with those compression results, and not knowing if the valves were originally taken in for the warranty service.... I just don't know. Thanks for any insight or advice! Very curious to hear anyone elses' similar experiences.