I have heard that ammonia will breack down the oxidation in some cases and allow you to remove it. You might be able to flood it via the seat tube. Were you able to remove one side of the BB or are both sides stripped out? Old school BB were removed with a different tool. The cup had two wholes that were opposite each other the key was then inserted into those and turned. You could try getting one of those and drill two wholes into you BB.