I believe that after all the soaking, heating, impacting, and swearing that you start getting to the drill out the bolt and try to remove the crank. I tried to get a patent drawing off the internet but no luck so far. That would go a long way in helping guide your hand. As you know one can saw off the crank and axle end with a Sawzall and a diamond dipped blade. That will go through anything. If the bottom bracket is of the same dimension as the modern one piece crank designs then replacing the original with a modern one piece crank would be very doable. I think going slow and consulting is also wise as you have been doing. You never know you might run into the Chicago Monarch bicycle crank guru who knows what to do.