Montana laws on residential security deposit etc... HELP?

We rent a house, and so far we have made the yard even better, have done no damage and it is cleaner than when we moved in. BUT, we can see from our continued experience with this couple who owns the house that we are probably going to run into a problem with them, they have become slumlords. We can hardly ever get ahold of them, they gave us the house in shambles, it was very very dirty. They screwed us by having us sign the lease two weeks before we moved in saying we accept it the way it was, and when we went to move in it was never cleaned after the last people. They said they were not going to sell it and now it is up for sale. They said if they did sell it they would give us a long lease the new owner would have to follow, now they won't give us the lease. We just know the deposit will be the next issue. What are Montana laws about this? Do they have to present us with receipts for a cleaning service? How can they within the law keep the deposit if the house is in better condition and how can we, and I'll use the words screw them out of our deposit if they begin to screw us out of it on no grounds reasonably? I am a law abiding person, my husband and I are both cops, but I am not about to go down without a fight, if they try and keep it I will pour paint on the carpet, I am furious. Don't ask me how I know this is coming, it will be as natural as breathing to them.