A lot of good information below, and I won't repeat it. But a few other things to consider or keep in mind:
I really, really do not like the use of price per square foot as a measure of value. It's a misuse of the data. It's fine if you're building a house. It's fine if you're remodeling a room or rooms. But there's so much that a price per square foot doesn't capture. It doesn't reflect condition of the property. It doesn't reflect age. It doesn't reflect where the home is located (such as on your dirt road). It doesn't reflect the home's layout. It doesn't reflect lot size. It doesn't reflect the presence or absence of a pool, to use your example. Instead, use comps. Comps will reflect all that: condition, age, location, lot size, and so on. Sure, you'll still run into some overpriced properties, but then you'll know that they're overpriced because you're using a good benchmark.
Next thing that occurred to me: You'll probably have better success if you narrow your search. You say you've looked at 90 properties in 5 different states. The market can vary county by county, and even by smaller increments (community by community). Try to figure out, within a radius of a couple of miles, where you'd like to buy a place. Then focus all your attention on it.
Next thing: Some sellers are unrealistic. They have inflated ideas of what their property is worth. It really doesn't help much to try to convince them otherwise. Just pass on that property and keep looking. Maybe, if the property is still on the market a couple of months later, the owner has a more realistic understanding of values. Or maybe not.
Next thing: I'm repeating what's below, but in some geographic areas, in some price ranges, the market is very hot. A good Realtor--coupled with your focusing on a particular area--will help you determine whether a market is hot and develop strategies for dealing with that.
So, in summary: Focus on a specific geographic area. Get a good Realtor--one who knows the area and the market conditions there. Be persistent.
Hope that helps.