1) I've replaced the whole distributor with a Cardone Select 841830.
2) Also, the gray connector on the ignition coil needed replacement, since the holding clip on the old one was broken. Apparently this connector is responsible for carrying current from the ignition key (pink lead) and supplying a signal to the tachometer (white lead). I used a Standard S562 i.e. this thing...
3) I readjusted the timing to what might be the factory default. I haven't found reliable documentation on what values the timing marks stand for, but now it's set like this:
The same symptoms persist as before, but now my tachometer is dead most of the time. Apparently white lead, or the tachometer connector it attaches to, is even more unreliable now.
The symptoms are less frequent though, I was able to complete a 25 km (15,5 mile) test drive without the engine dying at all.
Also, I noticed some stutters / surges while driving at about 100 km/h (60 mph). Another halfhearted guess, is the TCC trying to engage and failing?