" . . . ask if anyone could suggest an appropriate component to compensate for the pressure drop when the well pump calls for more psi. "
The well pump isn't calling for more psi; the system is letting more water flow out as more valves are opened. The characteristic of the pump is to deliver lower pressure when it is delivering more flow. Get a copy of your pump curve and you will see that if the flow is greater than about 150% of nominal capacity then the pressure will drop off quickly.
If you want more flow at the same pressure that you now get at the nominal capacity of the pump, then you will need a bigger pump with more horsepower. You might be able to put a bigger motor on your pump with a variable speed drive. You would get more pressure but not much more flow.
Before you add a bigger pump and an irrigation system you must determine the recharge rate of the well. You can usually pump a well for a few minutes at greater than its recharge rate, but you should never try to run an irrigation system at greater than the recharge rate.
Pressure booster pumps don't increase the capacity of the well. They only provide increased pressure and flow for a short time while there is water in the casing. After that you are limited to the recharge rate of the well.
From what I have seen of the Davey booster pump it is not likely to give good service. Others would be more direct and tell you that it is a piece of junk. Grundfos is a good name but they tend to be expensive for what they do.
You have done a lot of work to set up your system, and I would suggest that you consider the following to manage your irrigation and household supply.
1. Set up the irrigation controller along with the household system so that the household system has priority and the irrigation controller shuts down the valves when the pump is unable to maintain household pressure and flow demand.
2. Because the household demand is usually small you can probably ingnore the quantity lost to the irrigation system. If the household diversion is too much to ignore, then let the irrigation controller keep track of the flow or time and deliver the correct amount of water to each zone.
The result is that you don't need a larger pump and it won't affect you treatment system.
I would figure out how to divert all of the irrigation flow before it goes to the irrigation system. There should be no need to even filter it if you are getting water from a deep well.
I am rather surprised at the high turbidity that you report. Most drilled wells have a turbidity less than 1.0 NTU. Anything as high as 10 to 16 NTU is very turbid water. You will use a lot of filter cartridges if you filter your irrigation water to potable quality.