Seriously at my wits end

Look above the pan rail to see if any fluid is present on the case. Very difficult to do, you may need a mirror. If there is fluid above the pan rail, on the transmission case, you probably have something other than the pan leaking.

If thats the case, which part of the pan rail gets wet with fluid first?

If its the driver side, then you should look at the kick down lever, cooling lines, or selector shaft seal.

If its the passenger side, then look to the dipstick tube o-ring.

If its the rear pan rail, look toward the low/reverse piston pivot pin o-ring.