You would be amazed how logical most murderers and rapist are. There are many layers. Many of them may only be murderers in a specific set of circumstances such as a crime of passion, or in Clemen's case, a crime of negligence. Rapist are exhibiting power over others, but that may just be one facet of their personality. Layers.
With 3 staff, and 1 an ex-inmate, riot gear probably wouldn't be very useful vs 25 inmates in a riot situation. Especially inmates that are essentially allowed free roam of the facility (another real life reflection based on jurisdiction), free access to tools, fire axes, etc., as well as the wealth of materials available to make melee weapons. I've seen knives made from trash bags that would get the job done. There has to by a relationship besides authoritarianism for Fury to work. Andrews can still be a hardass, but he also seems like he allows Dillon to lead the inmates, and he also has to realize he has zero chance of escape if he pushes the envelope too far. It's actually a really interesting dynamic I never properly considered before. It makes the movie seem more real to me, and adds some depth that reminds me of the space truckers vibe in Alien.