.
...I hope I have enough old freewheels that I never have to do this again, because it was always a PIA. Having said that, I will repeat once more here that a 50/50 mix of acetone from the paint dept at Home Depot and ATF from the auto parts store works significantly better than PB Blaster as a penetrating oil on difficult to impossible jobs. It even works better than CRC Freeze Off, which works pretty well (also better than PB Blaster).

On the chain whip thing, have you tried making one out of bar stock and a (fatter) track chain ? That would be my next project if I were gonna do freewheels again. I think you'll still be able to get it to grab the outermost cog (but I haven't tried it). You can make the lever arm as long as you want this way. Use bar tape or something similar for the grip ends.