At the end of my rope. Pls help

O.K here is the scoop.
I purchased a 1996 E250 5.8L with 148k miles at a Government auction. I wanted a cargo van with enough cargo space and liked this Econoline because had a roof rack and contractor boxes in the back. Thought that I’ll get a cheap deal but I actually got a real lemon. As they say cheaper is more expensive sometimes! Here is why. First the van has rusted out underneath and there was a rust hole in the middle of the oil pan weeping oil. By now I know what it means to replace an oil pan on a Ford van – dropping the transmission and lifting the engine and all. I have also replaced the rear main seal, the tranny extension seal, valve covers, an injector, fuel and air filters, spark plugs, distributor cap and rotor, some of the cracked ignition cables, muffler, rear differential fluid, coolant temp sensor housing, repaired leaking fuel rail (dealer wanted $320 for rail), headlight wiring harnesses, speed sensor (I had the bouncing speedometer needle syndrome), tranny oil and filter, tranny oil cooling lines just to name a few of the repairs I performed. I spend more time lying under the van than driving in the cabin! Next I am replacing the inner and outer tie rods and the adjusting sleeve on the passenger side because the alignment shop cannot perform an alignment and in this condition the van travels all over the road and pulls to the left side.

However, I can’t diagnose why does the van die when I make an abrupt complete stop at a traffic light or a stop sign. If I do not release the brake slightly before the van has completely stopped the engine will just die and I will need to shift in Park and restart it. Why is that?
Also, even though the E4OD transmission has not been overfilled sometimes it leaks ATF from the plastic cover underneath the torque converter. When I was attaching the tranny after replacing the Oil pan I filled the torque converter with ATF thru the drain plug. It was the first time I ever removed a transmission from a vehicle and I thought that since I drained it previously I have to refill it. Is it possible that the leak is because of that? The tranny will shift only after I increase the RPMs when the van is stopped uphill. Is it possible that something happens to the ATF and it drains back on a slope and have to rev the engine up in order to drive?
Thanks for all the useful info shared here.
Simon