Camshaft Worn or Lifters? Metal in Oil Filter

Hello everyone,

I have a V6 3.0 engine (with approximately 270,000 km on it), and recently, out of nowhere, I started hearing a sound like a Lanz Bulldog with a single cylinder .
Then I removed the cylinder head cover and checked the water pump while manually rotating the engine. It didn't appear to be damaged, and I didn't see any metal shavings.
"Since I've been experiencing occasional misting around the engine and it's been having trouble starting, I decided to replace the injectors first, as they were due for replacement anyway."
Unfortunately, nothing helped. The loud knocking sound from the direction of cylinder 6 continues.
Then I removed the vacuum pump, but the knocking sound persisted.
Now, I took the head off and then saw that the hydraulic lifters for cylinder 6 are broken... I should have noticed it when I removed the valve cover the first time .
It is what it is; I'll just replace the crankshaft seals at the same time. The EGR cooler also always smelled a bit funny, probably because it was leaking due to bubbling inside the heat exchanger.
Now, to my actual questions:
1) Have my options expired?
I think they look good visually, but there's a slight "depression" that can be felt on the tread surface in front of the groove, both at the beginning and end.
"But Haarwinkel says, 'Can't you see!'"
I hope the pictures are okay; otherwise, I can send some more.
I would really appreciate it if someone could help me here.

2) I found metal shavings in the dried oil filter. However, I didn't find any signs of wear on the connecting rods, crankshaft, or cylinder walls.
I disassembled my HDD and took it apart; there are no scratches on the platters, and everything looks good.
Where could they possibly come from?

Best regards from the garage .