Hi Lucas,
"Your high mileage is reassuring to me; I think I can't really believe those theories about timing belts running incorrectly."
I removed the cylinder head to replace the head gasket and various seals. I checked the play of the ESP shaft by hand while it was still installed (not axially, but radially). I heard that the radial wear limit is supposedly 0.1mm. In my case, it's estimated to be slightly more.
Regarding the oil leak: replace the camshaft seal and, above all, the intermediate shaft seal

... it's constantly causing problems! I'm also going to replace the hydraulic lifters, valve stem seals, and the crankshaft bolt. Just buy the Elring cylinder head gasket set

– it includes all the seals (except the intermediate shaft seal). I bought the lifters for 64 euros on eBay.