So, the well purportedly produces 5 GPM. What does the existing pump produce? How many GPM are you hoping for at what PSI?
What are the pressure settings on the pump switch? If you hold down the switch, what PSI is the pump capable of reaching and what GPM will it produce at a higher PSI?
If you plan to aerate the water with a micronizer, 5 GPM isn't going to do it with good enough pressure. You might want to consider a system with an air pump instead. The greater disparity between what the well can produce and what you need, the greater the amount of non-pressurized storage you would need.
I get by with a 5 GPM of flow through my micronizer at 40 PSI but would like to see more.