PDR is usually for things like hail dents, NOT what you have in that door panel. The "dent" has stretched the metal. Heat and quench with a damp rag might shrink it enough to THEN work the metal into more of its stamped shapes. I believe that Eastwood sells a "metal shrinker" pad for a drill motor? What's in that door looks more like hammer/dolly work.
One thing I read years ago, with respect to "hammer and dolly" work, was to start at the edges and work inward toward the center of the deformation. A little bit at a time so that the resultant metal work is gradual and better-controlled. Might need to drill some small holes to remove some of the stresses put into the metal when it was deformed? Which would then allow it to be re-formed easier, using the least amount of filler.
Any time you take a convex stamping and put a concave shape into it, metal stretch will occur. It will take some finesse to get it back to convex, I suspect. Might have to end up at a higher-end restoration shop in order to get a really good metal worker to make it right.
Just some thoughts,
CBODY67