1) the flight departing to ORD will know that you and probably other pax are connecting, so they may wait for you a bit. These long haul flights have a bit more leeway compared to short haul, what is a 20 min delayed departure when looking at a 9 hour flight. Also if you check in baggage then it is even more likely that they will hold the plane for you. 55 mins is tight, but not impossible. February is not high season so passport control could be calm; this is where you may have to wait the longest though. Presuming of course your flight from LIS is on time...

2) usually passengers want to get to their destination sooner rather than later. They would likely route you via another route and of course rely on OW flights, so you may end up going via MIA, JFK, LHR etc. You risk having poor seat selection of course if any of these flights are full. I would not walk slow on purpose as it could be that they are holding the plane for you. Many times they announce the gate for connecting flights as your plane is arriving at the gate so that you know where to go / run to. If they announce the gate then they know you are coming and they are probably going to hold the plane for you.

3) I’m not sure but I don’t think you would be entitled to any compensation. If you do end up having to stay overnight then they may put you up in a hotel, that would be it.