Today I took out the IP vacuum regulator, cleaned it and visually inspected the diaphragm - not only did it look ok, but it also held vacuum quite well after I put it back together
(tested it with the thumb on vacuum connection method)

I also adjusted the gorilla knob a bit, I wasn't sure if it was too far in at the "running" position.

Sadly I couldn't try to start it afterwards, the battery's empty. But I was going to properly adjust the valves tomorrow, and replace the two other faulty glowplugs, maybe they somehow affect compression? Wouldn't surprise me with bubbles already forming at the seams

Oh and FYI: the idle adjust screw still had factory paint on it - I don't think it has been turned.