Drill hole in pan and install say a drain plug kit from B&M transmissions. I don't use that exact plug, I cobble mine up, long story there. The B&M will work.
I see nothing wrong with 10 seconds at a time as long as you don't run it dry. By the time you get air at the tube the pump will have possibly scored itself since a long distance between. I'd err on the side of trying to leave at least one quart still in trans.