Greetings. I have some familiarity with this area, more so on the NE side of the MO River. Donald D Studey did time in the Nebraska State Penitentiary for 18 months (April 1963) for check fraud. Seems that was a common crime he commited across many states. He also may have been in the service sometime right out of high school; where he was visiting family in Nebraska City, Nebraska in the early 50's, quoted: "home on furlough". In the 1963 court conviction, the judge chastised him for being a poor father and provider, and described him as a "drifter". He had a borther/cousin/etc. living in Gillette, WY by the name of John Studey. Yes, he inherited the land, his father Ira, owned it previous to that. The Study family is rather extensive and has been in the area since at least the 1850's.
As goes wells, it is not uncommon to confuse a well and a cistern; both can have very wide openings. There are hand-dug wells, and there are also "sand point" wells (these are too narrow an opening for our purposes here). Sand point wells are more like our modern wells, and generally employ a windmill, pump, etc, to extract water. In any case, 100 feet for a well isn't particularly deep for a sandpoint, but hand-dug---that's pretty deep--it would be very very challenging to excavate. In the case of this well, I was under the impression that it was at the edge of the property line on the east side of the parcel (The parcel is irregular shaped). Looking at a 1950's aerial photo; it does appear a farmstead/outbuildings stood in the general area of the trailer.
I would venture a guess that it is a very old well, and likely belonging to a one-time homestead that is no longer there. This area is called the Loess Hills, because the hills are comprised mostly of Loess. This soil is fairly compact and is wind-blown in origin, and can be kind-of be "cut away", it has very little rock and gravel typically. As goes the culture of the area, it is important to remember that relatively few people live in Fremont county. Families have been there for generations. If you decide to go after someone as a serial killer, you better be 100% sure, because everyone will know you made the accusation. If you are wrong, it will stay with you for life. Why? Because there are so few people there, and so much intermarriage, that you will be a social pariah forever. Why not just move then? Because, most of the people there are attached to the land (often times inherited) for agricultural purposes, etc. Generally, you'd be asking people to move away from their source of income and families---so I think that it is possible that something could go on unabated.
I don't know about the 50 to 70 number, but I can say that Omaha has a very long history of organized crime and prostitution, but by the time of the 1960's and on, crime and prostitution was far less "organized". Assuming he did this, and was active in the 1960/70/80's, I would think it wasn't just sex workers, but others as well.