Help! 100k maintenance on 3rd gen

Doing a 100k mile maintenance on my new-to-me 2018 TRD OR. (3.5 V6)

A few questions:

There was some dirty oil/gunk on the inside of the intake tube, the end of the air intake where it connects to the throttle body (pictured) What could be the cause of this?

I believe I need a new throttle body… it’s resting position (closed) is 2 to 3 degrees off true. See pics.

I bought the MAF + Throttle Body Cleaner combo pack, and accidentally sprayed the MAF with the throttle body cleaner. I followed up with the correct MAF cleaner. Am I okay? Seems to be driving fine.

Drained and filled my transfer case fluid, but I forgot the washer on the drain port. Am I okay to leave as is?

Lastly, I am unsure that proper, timely maintenance was kept prior to me owning this truck.. I just did a drain+full on both diffs and power steering, new serp belt, oil change, tire rotation, new filters, grease joints. Prepping to do spark plugs eventually… anything else I should be doing or Team OilDrip videos I should be watching??

Thanks in advance!