Shoe- We are hooked up to community water as of today.
We have discussed the well situation with many other people, those who know more about the situation that we do. They all pretty much agree that our driller was in over his head with such a deep well, but that it is possible for us to get good water out of the ground. However, this guy has been drilling for a long time, so....it's hard to know what to believe, except that no one knows what the problem is.
We're still using the (3rd) well for irrigation of everything, so that's something.
We are still deciding for the moment what to do long term. We can risk trying for the 4th well, and still might. Right now, though...it was more important to just get the clean water.
Wells that deep are very expensive, and not at all something that we would try unless we are convinced it could work. There are 2 aquifers we can reach- the first is at 300 or so feet, but it is extremely high in iron, and so not suitable for household use. The second is the deep one at 700-750.
The sand the well pulls up is so fine that it passes through the screens, the hundreds of gravel packs they put down, and the sand trap. On the second well, it even passed through a very expensive filter (we didn't try again with the 3rd one).