Some barstard kicked over my lads bike while he had his back turned and bent his mexh hanger about 30 degrees off the straight. The lad needs a mode of transport...
If I try to straighten it, is it likely to straighten and shift accurately?
With luck it may, otherwise your LBS should have the correct tool to get it exactly right.
Big adjustable spanner and close one eye. Bent mine on my old "that blue" one years ago after a good smash. Bent it back into place with a big adjustable from the tool box. Still goin strong about 4 years later. The hanger is nice and bendy.
The thread on the mech pivot is the same size as the threaded axle in most cup and cone hubs, so, ideal tool is an old axle- thread it in, and it's nice and obvious when it's straight. Adjustable spanner works too but depends a bit more on having a good eye
I think the mech hangers on on-one's are made out of cheese. I had a plate welded onto mine to stop it constantly bending.