Useful bodge-it tool for the straightening is an old cup-and-cone axle- the thread is the same as the mech bolt, so you screw it in and 1) you’ve got a nice lever and 2) you can easily tell when it’s straight. (if you want perfection, get a bit of threaded rod or similiar and stick it in the dropouts to give you a comparative straight line.
Now… Not sure about this but gut feeling is that heating it up isn’t required but should reduce the strain on the dropout? Obviously steel’s pretty bendable and durable but it’ll weaken eventually… Anyone confirm or deny?