Interesting development. Usually my 40w iron is enough but not always. If I lived closer I would let you borrow my 100w soldering gun. I have only ever used it to remove solder from some boards and to repair the connection to the thermalcouple on my water heater.
Ok, here are some other creative ideas. Not sure if they are good just creative:
- Use a sharp chizel or something to scratch the solder off. This could result in ripping the pad off the board.
- Borrow the blowtorch but don't use directly on the solder. Try using it to heat your soldering iron a little more.
- Use a grinder, dremel, hack saw etc..
As long as you remove enough of the old to allow yourself to get a good new connection you will be ok. You should be ok just using your normal solder/tin when you connect your wire again. My old i3 Migbot used a MK2 heated bed as well. I used normal solder/tin on it and was able to get the bed up to 95 C consistently. it held fine.
EDIT: you beat me to it. Nice work.