ORD is my home airport. I've flown in/out numerous time and I can say that whenever I arrive ORD, it is usually at one of the farthest gate. As soon as you walk out of the plane, it will be about 10 minutes, at a brisk pace, to get to the ATF (TRAM station), from there its about 5 minutes to T5, and another 5 minutes to get to the security area. Right there you have 20 minutes in transfer time, not counting how long you have to wait to get to the gate after landing, get out of the plane, wait for the tram, go through security, get to departure gate. The 20 minutes in transfer is for someone like me who is familiar with the airport and know where to go, I'm not sure on your situation.

Someone up-thread mentioned the bus connection from T3-T5, it wont be an option for you as I believe it stops working after 7 or 8 pm, someone else might correct me on this. Last month I had a 3hr delay on my AA LHR flight, got re-booked to BA at the flagship lounge, so I had to go to T5, I asked where I needed to go for the bus, and the attendant mentioned that it stops already. I would suggest 90 minutes, maybe longer, the one flight you do not want to miss is the international one, more so since it is the last one of the night, and there are no other alternatives. It is best to arrive ORD earlier. Good luck.