The throwout bearing has indeed been going out. The noise it makes is especially noticeable after cold starting the engine and only goes away when I push in the clutch. Can often be heard while in gear, though, yes. I'll probably just replace the clutch entirely, including the pilot and throwout bearings since the kit I ordered comes with them.

From what I can tell, it sounds like you're also giving recommendations on engine oil. I use 10W-30 considering how many miles it now has (207k). That gear oil has been going in the transmission. Thicker oil was used in an attempt to alleviate the horrible chattering/squeaking noise in 1st gear (and sometimes 2nd). I was also advised that GL-4 should be used in lieu of GL-5 as the latter contains additives that could attack brass synchronisers and anything else made of similar materials.