It's safe to say that this proposed agreement is unreasonable, but it sounds like you already know that. The attorney's fee provision is completely oppressive by itself because, based on your post, it allows the landlord to charge you an unlimited amount of money just because they feel like it. It would not be wise to agree to such a proposition unless you have a very compelling argument that that provision is invalid (and you are confident a Court would accept that argument). Note: I am not expressing any opinion or advice on whether such an argument exists.
I'm not going to do the research for you right now, but I suggest you research any legal theories that might allow you to recover the $850 you paid. Did you sign any specific written agreement governing that $850? If so, the following argument will be harder, but you could still possibly argue that the agreement governing the $850 contained a covenant providing that the form of lease agreement would be reasonable in the sense of being broadly similar to leases commonly used in the local rental market. If there was no written agreement governing the $850, that argument will be a lot easier to win with, but even if there is a written agreement, you can still argue that such a covenant was necessarily implied; after all, it's basically a scam to collect $850 application fees followed by presenting a ridiculously unreasonable lease that no one will ever agree to, allowing them to collect $850 fees repeatedly.
Again, I have not done any research of Missouri law, and this post is not advice, just suggestions on things to research.