I don't know if this problem has been resolved, but it sounds to me as if your transmission is shot.
What seems to be happening is that there is a good bit of debris in the sump and it is stopping the filter.
Scenario: Crank car and drive a short distance, suction pressure sucks all of the debris into the filter and stops it up. When you switch it off, the fluid washes the debris out of the filter and you can move again briefly.
If that is the case, all of the diagnostic driving you have been doing is sure to have further damaged the internal components. Not to worry though, if the filter is stopping up, you already needed a complete overhaul or new tranny.
Good luck and update us.
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