Detecting Open Circuit, Short Circuit and Battery Reversal
I confess to have understood only part of your questions. Anyway I will tray to share my (small?) experiences.


For the reverse protection my suggestion is to apply to the pins D and S of the device a simple resistor and a LED in the reverse polarity. It will light when the polarity is reverse. 


For the overcurrent or short circuit, if you don't need a very quick response, I want suggest you to use devices as Polyswitch. Applying in parallel to it the usual resistor and LED (in the direct way) you will see to light it when the current it's been behind the 'Trip current' for enough time to turn the Polyswitch in the open (not absolute) state.



I hope that this my answer will be useful to 'tune' me into your problem.