A concern is you have a rather complex bend in some stout steel. As you straighten it out, those 2 parrallel straps may no longer be parrallel and it will be very difficult to line up your wheel shaft any more?
If you had access to a 20 ton press, this would be an easier repair. One can slowly press things into place, stopping and correcting as you go.
With heat & a hammer on such a piece of metal with limited anvil and experience, you might be in over your head to get this 'right'.
If you have independent welding shops by you as I do, the cheapest would be to take it to one of them, about $75 or less would get it either straightened or the top bent piece would be cut off and replaced with new, everything kept lined up.
Perhaps I'm stating the obvious as well, but I think you will have a very hard time getting the multiple bends out and keep both arms parallel with what you have.
If you are heating, you just keep the tip moving, make bigger circles with it, keep covering more area, come back briefly to already heated areas until it keeps getting hotter, and bigger area. Can take some time to get a big piece thourghly heated, gotta move the tip a lot but slowly, it becomes a pattern to keep working in more surface.
I work with oxy-lp as some mentioned, be safe with the acet. gases as mentioned.
--->Paul