[MB190E2.0]

Re: Certainly not my first DIY job, but it is my first on a German. I'm used to working on Jap

There's still a clanking noise that I suspect is the timing belt, but I won't make any judgements until I've got the fuse installed.

I have got the same noise in my car as well.
My guess is that the tensioner pulley is ready for replacement.
Listened to it with a stetoscope device. Heard a loud rattling noise coming from it, also the alternator made some rattling noise.
I would try running the engine without the auxillary drivebelt It is certainly my first priority when I get the time. Good Luck.