That "extra leverage" (ie. steel pipe) worked like a champ. The last two bolts on the rear transaxle mount came right off, and I'm ready to drop the transmission at this point. After looking at the jack I was planning on using to lower the transaxle, I decided against it, and ran to another local supply store to grab a transmission jack adapter for my existing jack, to make sure I pull it down evenly (and more importantly, can put the sucker back up there).
Total time invested so far: 12 hours.