It wouldn't hurt to do the whiting thing again. You did not say how long you treated this stock with acetone and whiting.
I had a similarly discolored stock that had a little oil in it. I used powdered marble (calcium carbonate, same as whiting) I got from an art supply store, $8 for an 8 lb bag. I put a couple inches of it in a suitably sized cottage cheese tub, put the stock head in it, wrapped it all up (to keep from making a mess in case it was kicked or something) and put it in a warm corner where it was to be undisturbed. After about 2 months, I took the stock head out and vigorously brushed off the powdered marble that adhered, inspected it, then returned it to the powdered marble for another couple months. After about 4 months total, what oil there had been was gone.
You could rush things, but you won't get as good a result.
