A 1000 gallon storage tank is not going to last very long when irrigating. At 15 GPM it will only last for about and hour. Your real storage is in the well. If it will make 15 or 25 GPM indefinitely, then you don’t need a storage tank.
In the past over-sizing a well pump was not a good idea, because it would cycle on/off too much when using smaller amounts of water. However, a Cycle Stop Valve will let you install as large a pump as you want or need, and will make it work like a small pump when a little water is all you are using. And because the Cycle Stop Valve stops the cycling and makes the pump produce exactly the right amount all the time, a 4.5 gallon pressure tank is all you will need.
Congratulations on the good well. Now put in a pump system with a CSV so you can utilize the well water at any rate for any length of time you want.