What should I do if the pressure is too high in a home water pressure increasing system?
I think my first step in sorting this out would be to positively identify the feed from the supply main, shut it off at the main, cut this whole business out at least temporarily, and connect the house to the main without all this "stuff."

If, as appears to be the case, the pressure from the main is being reduced before it's increased, something is just plain odd, and it costs a lot of electricity to be that odd, not to mention the complexity. Put a pressure gauge on it and see what you actually have for pressure before concerning yourself too much with this mess. 

An alternate possibility is that this is supposed to isolate the house from times when the supply of water is not there at all - in which case it's a poor job of designing a system for that purpose, IMHO. Does your water utility fail to provide water on a regular basis?