You should be able to easily get another 15-30 horsepower with a mix of cam/flash/exhaust on the stock heads. You may need to use higher octane, but I doubt it. If you're going to tear it down and don't mind changing to LS6 heads, I'm sure you can get more. I've heard good things about HP Tuners for engine management if you want to change and want more control. Porting the stock heads should do the trick as well.
Don't use Dorman knock sensors (or anything) as they have a bad rep. The knock sensors have a rep for going out as they like to trap moisture in the recessed holes they screw into, I've already had mine done too.
You can get a wireless Bluetooth or wifi OBS code reader dongle that will connect to your phone. If you use an android you can use Torque for free to read your codes and see engine parameters in real time. I got a generic OBD Bluetooth wireless dongle for $10-15 five years ago off ebay and it is the best money I've ever spent. Borescope cameras that connect to your phone are dirt cheap ($10-20) too.
Sams will polish the lenses and put on a protective coating for $35 with a warranty last I checked. They are lazy and you'll need to make an appointment so YMMV. If your housings are too damaged you can buy new housings off Rockauto or Ebay cheap too.
Texas Alternator Starter Service in Austin rebuilt it. It cost just barely more than an autozone Gold rebuild and I wanted to keep the original part seeing as it lasted so long.
I pretty much agree with your research and don't disagree with anything. I've been meaning to get my oil analyzed and may go ahead and do it next time I get it changed. My biggest problem recently was a persistent cold start lifter knock but pandemic speeding and the higher highway rpms have really quieted it down (I think). I'm pretty sure when she dies it will be because of a collapsed lifter, a wiped cam lobe, or the rings. Still love this truck.