What could cause AdC Reading only to get stucked?
You appear to have a difficult problem.  One of the rules I use is never power the arduino with 5V power, always use the barrel connector and go with about 8 volts. The additional filtering etc the on board power supply does is amazing. The external 5V is ok for most of the other devices. Another option would go to the local electrical store and purchase a metal junction box and mount the electronics in that complete with a metal cover. Be sure it is grounded to earth. The reason for this is your prototype assembly has a lot of antennas that will pick up just about all of the electrical noise in the area. Remember all grounds must be connected. Arduinos are not hardened for industrial or commercial controller applications.