Injection pump problems/idle/stall/vibration

Hi All
With the recent injection pump/idle problems posted recently I figured I matters well join in...
1980 300 SD, 500000 miles, compression 350-400 neighbourhood, (excellent), starts well, little smoke, etc

1. Engine will stall and is very hard to restart, first occured after a hard corner, but now it happens anytime
2. Idle is irratic, will be at 800 sometimes, then 1100 the next time it returns too idle
3. Engine vibrates alot, you can see the whole front of the car wiggle!

I had it into my trusted mechanice of 25 years and they said injection is DEAD "nothing to adjust" Are they kidding? There are alot of adjustments as mentioned here, but my question is, are these symptons caused by one thing or a combination of a couple of problems?
The fuel filters are frequently replaced and always have fuel in them. The line going to the pump will almost empty itself when revving the motor though, seems funny cause in park it uses alot less fuel then full throttle up a hill-could the pump simply not suck enough fuel anymore? Should I install an electric pump to aid it (don't ask, I have seen it on VW diesels)
I have done and redone the valve adjustment...concerning vibration
Is this "gold" screw as mentioned in earlier posts purchased from the dealer or here...
I am willing to try anything at this point, I really find it hard to believe the pump is gone.
I realize the car is old and high mileage, but the engine is perfectly clean and runs 100% otherwise, capable of 40mpg! It has great power in all conditions, cold, hot, uphill etc, but it will just stall all of a sudden, usually when coasting, light throttle, rush hour, hard cornering under full throttle.
I have owned the car since 1986 and 80000 miles and it is well maintained, but this stalling problem is getting to be too much. I do not want to throw money into a pump rebuild and find out it was an air leak or something stupid later...
Plus the rebuild would outway the cars value at this point.
Your help is greatly appreciated
Greg

[SW]

Wow, 40 mpg. I wish my car could get that kind of diesel mileage. I think your car does have a elctric fuel pump, the hand pump sits on top of it. Maybe if this pump is going bad, your injection pump is not getting the fuel it needs?

I have not seen any electrical connectors/leads around the pump or hand pump, I do not think there is an electrical pump but...
40 mpg is only at 50 mph and no faster, I live in a small town in the country...I have a well trained diesel light foot!
30 mpg is more realistic (when keeping up with traffic)