In theory, the attic temperatures are not an issue of concern. The roof ability to vent the moisture is what is the critical element.

Yes, zoned AC systems that are in the attic do have to work harder if that is the case, but speaking purely theoretically, the temp is not the issue if your envelope (air) and insulation layer of your attic floor are intact and sufficient.

You will always want to have more incoming air than you have exhaust air. If not, you run the risk of creating a negative pressure in the attic and thereby removing conditioned air from the conditioned zone below. This is what is often happening when people run attic fans and feel like they are "working" by keeping the attic cooler.

They are, but at the expense of sucking conditioned air into the attic.

I am guessing that you have soffit vents for the incoming air? Have you checked them and are they unblocked and open? If they are and you have good continuous make up air coming in, putting a couple of vents in the roof (not powered) is okay if you are concerned.

Again, it is not really a necessity if your attic insulation and envelope air tightness is good. If you are worried about a second HVAC system running in inhospitable environments, a little more exhaust to get the air moving shouldn't be too back. That being said, even a small ridge vent should flow plenty of air. Check your soffits.