If you only have four of those .8 GPM heads running at the same time, and the pressure just hovers at 58 PSI, then I doubt you have enough pump to run the pressure switch up to 50/70. Also if the pressure is hovering at 58 while running the smallest zone, then I doubt cycling was the cause of the pressure switch melt down. Maybe you did just have a bad switch.
To run all your sprinklers at once operating at 30 PSI will nearly cut your electric bill in half compared to running half that many at 58 PSI. You get more water per KW of electricity when running at the lower pressure.