This is to verify that the best way (and probably only) way to do this if the tranny is in place, is with a small Jabsco pump inserted in the dipstick hole, like you have been doing. The drain hole at the bottom of the tranny is not accessible in our boats.
Even if it were, we run the risk of stripping the threads when screwing the plug back in, and of not seeing a possible leak if there were one because the plug was not threaded in correctly. The guys at Transmission Marine in Ft. Lauderdale, where I take mine to be serviced, have instructed me to use the pump. It takes very little oil to fill that tranny, so just about a pint of oil, maybe less, should come back out. Hope this helps.
If you removed some already, put your dipstick back in and see what kind of reading you get, maybe you already have all of it out.
