Hi Melissa
Sue asked me to look at your Illinois family today. So I did. Looks like you are doing fine with John and Isabella. It is John's father that is your sticking point. About 1 year ago I did research on the Corkill's in Mona, Ford Ill for another responder on the board. I am quite sure that the John you found there is not your John's father although the ages are close. There is a whole different family that emigrated there. At this moment i can not put my hands on the work that I did. I will look for it to be able to give you more info on that particular John and why I am sure he is not the father of your John. Good luck with the rest of your research.
Carol G