Don't use a vice unless you can't find/have access to the correct tool. Use the derailleur hanger tool. The threads in the tool will protect the hanger threads, it'll keep the face of the hanger "planar", and you'll bend it back in the correct plane.

When I worked in different LBS's we'd regularly bend them back from similar conditions. Dropouts are made of mild steel, and can be bent back without breaking as long as you don't do it more than a few times.

A few years ago I bought a donor bike for my daughter in the same condition. The derailleur was actually sheared off, but the hanger held on, and was bent back like yours. Here's a before and after picture:



Although the hanger isn't used (I built an 8-speed Alfine IGH wheel for this bike), it's in perfectly aligned position. Some day we may want to make it a derailler bike.

Even if the hanger was removed, you could still braze a new one on without removing the entire dropout. Been there and done that too. Probably someone had a bent hanger and decided to hack it off:



One repair you can do yourself (someone's already offered use of a derailleur hanger local to you), the other you'd have to pay a framebuilder to do.