most of the stresses in cold rolled are concentrated on the out skin, get 50 or 100 thou in and most of it is gone. When you do get banana like warping its usually because of taking it from one side, i.e. you've milled a piece on one side which has changed the equilibrium of materials' internal stress forces - the warping then can be quite dramatic.
I'd think you'd have no issue with the crank however. You are removing material equally and enough of it that the worse affected areas will be made into chips. I'd do it between centres, and switch it end to end a few times to get where the dog was holding it.
For rectangular stuff, I do iterations of flips in the vise, one side then the other, without taping the work down (which will remove the banana shape until you release the vise again). I've also stress relieved it in a controlled oven with ramp cycles which works, but takes more time and the resultant scale is somewhat of a pita. You could also get 1144 "stressproof" which about the nicest material and ideal for a crank - much higher tensile strength than mild steel, free machining and minimal stresses
