rubber pipe under car not connected

That "little box" in the back is the rear differential. It is a gear box and it contains differential fluid (oil). There is one in the front if your Jeep if it has 4X4, and most do. That rubber hose is simply a venting tube that clips to something above and got knocked loose. Hook it back up but leave slack as the differential moves up/down on bumps. If it can be driven, go to auto parts store and scan for codes to see why it stalls. Or borrow a scanner. It can self scan too. Turn the key from "Off" to "On" three times quickly without starting the engine. Stop at "On". Your codes with show at the odometer display. It will show "done" when it's done or if there's no codes. Google these codes to see what's wrong. If you happen to get "code 0320", there is still a problem with the crankshaft position sensor. They have to be installed with 0.030 inch clearance to the flywheel.....very close but not rubbing.