What a week for me to go on vacation. If I were at home, I would absolutely come to Midway and help you make your Chicago connection. Unfortunately, I am in Arizona until Saturday. Pat had some good suggestions about enlisting the help of airport escort services.
I'm sure you've either thought of this or have been told this, but make sure you have a harness for Levi (instead of a collar) when you pick him up. I flew with Riley (my SM girl) shortly after her decompression surgery last year, and she had no problems with the pressure changes in the cabin. She has flown many times since then, and has done great. She has a titanium mesh implant which I believe LIVS does also (actually think they were the ones who pioneered it) and she has never set off the alarm when going through security. The first time I flew with her though I was nervous about it and had them hand screen us rather than having her go through security. Because I had a note explaining the implant, security personnel were very gracious and complied with my request. Since then, I just carry her through security. Take off her leash and harness when you do though. Good luck Kathy and please let us know how it all went.