Can’t clean nozzle with it on, and taking it off requires a tuning for it to heat properly. It needs to be heated to clean it. So I don’t see the point of a silicone sock, at least not on this copper heat block.
That might explain the burnt filament, it does explain the black spots. Also, need to raise temperature to at least 240C. The prints should look better at that temperature, bridges might be worse though. And need to reprint retraction test, with the new temperature. Except, the retraction test is mostly useless, hard to tell what is good or not good. Maybe increments of 1 is too much.