That’s curb rash, and looks like a wheel not a hub cap. Can’t really get rid of it without refinishing the wheel. It’s very minor and won’t affect anything.

I would absolutely go back and do that. Lube the contact points where the pads sit in the bracket, and the back where the caliper touches. Without grease, the pads and can seize into the bracket and cause uneven wear/wear our way faster/overheat etc.

This all sounds like normal operation.

60 to 80kmh but RPMs literally do not move until say around 2300RPM

You’re likely in a high gear, so a small engine rpm change makes a big output change. Give it more pedal and you’ll force a downshift, which may be what it’s doing by itself eventually giving you the expect rpm rise.

the RPMs suddenly rise by 500 or so as if the car downshifted, but you see I have a CAN datalogger and am logging the gears, the gearbox reports it’s still in 5th gear

This is absolutely the converter unlocking.

Most vehicles will set one of many codes if they see any sort of transmission weirdness at all. If you’ve not go codes setting it’s almost certainly normal.

You don’t.

They said that they don’t know what the error codes are and that their OBD reader just diagnoses the problem for them.

Lol good fuck, never go back there again. Yes there’s lists of codes and their corresponding diag charts in the vehicles service manual. You can subscribe to somethjng like alldatadiy to get all tbat info.

I’m not familiar with that vehicle specifically but did it require dropping the pan/filter to replace?

I’m going to assume from the no info anywhere that those are the lines going into thr firewall, you’ll need a heater core.