I'm surprised the Callisto didn't get the job done.  It sure works "here"

I would not be worrying about stunted pigweed in corn over about 3' tall, even if it starts growing well at this point it is not going to be able to do too much damage.  We had a lot of escapes last year and the weather pushed us out of the field as we were about to finish cleaning it up, there was no effect on yield.   In fact we joked all harvest that we needed more pigweed because the yield tended to be highest where the middles were full of pigweed.