I drive an 85 turbo diesel jetta, although its stuck waiting for injectors right now, and a clutch job

In my limited experience, I got mine with shredded intermediate bearings which I have since replaced.
I had that oil buzzer go off on me on a sudden right turn at 20mph one day, but it continued when I hit the next straight away so I pulled over. I had some oil with me because the car was new to me and when running it had a constant drip. This is the way I picked it up and I drove it for a few weeks so I assume it took that long to be low on oil.
It went away with a quart fill in that moment, and I was watching things more and it never did it again, either on freeway runs or an a up/down 20 mile hill ride.
I have not relaunched the car yet, but I atleast got rid of the leaks and have replaced the main seals for the heck of it thus far.
So that probably doesn't help you at all, for all I know mine don't work properly

As far as that glowplug light, I had seen a little of what you describe but after reading these forums a bit, I knew I was going to "pimp" my glowplug system, and also I totally deleted my water seperator unit under the passenger side backseat underneath the car. I then started fresh with new soft lines from the tank to the solid plastic rails under the car, and soft lines inside the engine bay. For me I had to do this because everything was original with leaks, etc.
I cut the wiring harness and taped up each wire lead and zipe tied them up. I don't get that light now unless its the typical wait to start phase.