I've tried that, but often it seems to slip out of the vice for me.

It worked! Wow, did that take some torque!

As you can see, I used three or four more washers than I needed.



I was surprised how much work it was to get this thing apart after it was out. And I was really surprised at what it did to the washer.





Is this typical? I also can't put the nut on past where it was for the removal. I think my wonder tool may be shot after only one use.

I've definitely damaged some of the washers similar to yours with vigorous use of this tool. Not the bolt or nut though, although it certainly seems possible.

Has anybody tried using a left handed thread bolt? This would tighten itself up when removing a RHT fixed cup - the preferred outcome.

There is no need for a left-threaded bolt. You just turn from the other side to reverse direction. On French and Itallian BB's you insert a socket through the BB shell.