Re: EGR & burned valves - I see no way it can happen!
I'm not sure on your system - I don't have one like it. But if it's a vacuum actuator there may be a screw adjustment on the plunger - look for it.
Some actuators you just loosen the mounting screws to adjust.
Some you bend the mounting bracket.
Look on the linkage that contacts it too - there may be an adjustment screw there.
Recharging the system should not make a discernable difference - the load is mostly the compressor turning.
The idle up system is there only to prevent stalling due to the extra load. Properly adjusted it will restore idle back to what it was before the air conditioner was turned on, or slightly higher.
EGR's are used to lower combustion temperatures. NOx forms about 3000 degrees - normal combustion temps are slightly over that "magic number." Adding a tad of inert gas, helium, or burned exhaust lowers the combustion temp slightly. Essentially it spaces the molecules farther apart, not unlike spacing barbeque charcoal briquettes slightly apart to lower the temp.
Engines that were not originally designed to have EGR usually fare better with it disconnected.
But engines that were designed, or the heads modified to use it need it to work. Otherwise the slightly hotter chamber will have pre-ignition - you may not always hear it, but it's destructive.
EGR only operates under cruise conditions anyway -- unless someone that doesn't understand changes things. At idle and lower R's the EGR valve stays closed. At cruise - mid RPM range it opens, letting a tad of exhaust in the chambers. When you punch it, -- Wide Open Throttle, it closes again.
EGR is unrelated to air conditioning fast idle.