I believe that strip w/contacts at the end is a protection device (bi-metal) for the guages when a surge may occur at startup. The screw is factory preset for adequite tension to close the circuit. My '88 Trooper has it on the temp guage but in '89 it was moved to the fuel guage. My Troop had dead fuel and temp guages until I removed the cluster and cleaned those contacts.
I too had eratic fuel readings (which was better than NO readings) and pulled, cleaned and adjusted my sender with minimal favorable results. Seems Isuzu has been plagued with fuel sender issues, but each one has its own peculiararities and can be understood by the driver in time. If every vehicle had to have a qwerk I think I'd rather have it in the fuel guage than, say, front suspension or transfer case!