Agreed on Crutchfield and I did use their BOSS unit years ago but purchased the entire adapter set at the same time. It was a relatively easy install using their provided harness.
If the issue comes back you could try to snake a thin weed trimmer cord up the drain from below. If that shows up inside the 'box' then you should be good. If the cord shows up elsewhere that would be the point where the disconnect happened.
Wheel bearing. Likely the right side since the slight turning motion unloads the bearing briefly. Time to get it replaced for sure if you can hear it that clearly.
If it is like the older gen then end of the drain is hidden behind a heat shield. If you run the AC with the vehicle lifted for a while you should be able to spot the drips perhaps?
A drain and fill is different than a complete flush. Usually a drain and fill will replace just about 3 quarts or so. This is enough to re-fresh the fluid. A complete flush involves using a machine and pumping out all the fluid and replacing with new. If the flush is done on a regular schedule...
Is a return possible and get one from a place that does provide a harness, or has that ship sailed?
At the very least they should be able to give you steps to hard-wire the unit. Very poor customer support in my opinion.
What kind of new stereo are you installing and where did you purchase it? I am asking because I installed a BOSS Carplay capable new unit and I purchased it from Crutchfield. They provided the custom harness I needed and it was plug and play for me. Perhaps you can reach out to them regarding...
An OBD reader will now show 'module' errors, if any did occur. You need a scanner that speaks to each module and retrieves the manufacturer codes. There are Launch scanners on Amazon that perform this function and if you plan on keeping the car for some time and are somewhat DIY it may be worth...
Are you sure that the oil is not coming from higher up on the engine? The reason I ask is that is the cylinder head you are looking at and the likely hood it developed a pin hole is pretty remote but it is possible. Higher up on the engine you will have the valve cover for that head and they can...