'89 MBZ 300E won't start

My car has needed a valve job for years. One plug always gets corroded after several months. When I need to get a smog certificate, I replace the plugs (Bosch Platinum) immediately before the test and always pass
(with the exception of the gas cap, and a catalytic converter recently put in).
Just recently, the car would start perfectly and rev normal in neutral, but would stall as soon as it was put in drive. I haven't been driving much lately, but when I would, I would have to get high revs in neutral and slam it in drive to get it going. That would still stall most of the time, especially if the car was facing uphill. After hassling this scenario for an hour or so, the car would stall less when warmed up. Notwithstanding, the car would always start without a problem.
I assumed it was the plugs as I haven't changed them in a long time. After not using the car for 3-4 days, I removed the plugs and cleaned them. (My car was blocked in a parking lot, so I couldn't go get new ones at that time.) I reinstalled the cleaned plugs, but did not tighten them all the way, knowing I would be removing them again in a day or two. At that point, the car just turned over until the battery (and bu battery) went dead. I replaced the plugs with new ones today (Bosch Platinum). I first removed each one and turned the car over a few times being paranoid that loose particles from my scraping may have gone in the cylindars. However with tightly seated new plugs, same result -- turn over and over without catching until batteries go dead. I even used another running car to jump, in case the batteries did not have the juice to initially start it, but no go.
I read through past postings and jumped the balaster resister (half the outer case is missing, though it is still connected), and jumped the fuel relay on top of the red electronic device (sorry, I tried to get a Chiltons and checked with the dealer and cannot find a manual, but just learned about the CD here). Another post referred to the red part as a fuse, but stated it was on top, mine is on the side. Also, with all the gas pedal pushing, I'm not really smelling the gas I would expect. It is acting like it is out of gas, but the meter shows 3/4 full.
Lastly, while informing me of what usually causes the symptoms I described, keep in mind that I suspect foul play may be involved.
Thanks in advance for any input you may have.

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