Unlike aluminum dropouts, the steel dropout should be able to take the stress of bending the dropout slot tip back to normal. If there's any weak point it would be the adjuster hole at the back of the slot. I'm thinking, if you can brace the back end of the slot, near the adjuster hole with the exact sized shim so that end that does not need bending will not be stressed too much, you should be able to avoid breakng the DO....
I've heard of builders heating up the DO to make it easier to bend it back, but unless you know what you are doing, you might end up damaging the DO and the frame, and the frame's finish if you heat it yourself.