I must make a few comments.
First; if you start shooting long distance at a perceived threat without knowing their intentions, you will be the criminal. If you are being shot at, then defend yourself, but don't pull out the ole' Sharps and blaze away at a simple intruder.
Second; Based on the guns you mentioned, revolvers and a rifle, you have more than enough to defend yourself "if" you know how to use them. I agree with many here who suggest a good basic pump shotgun. It does not need to be tactical or even cool, just dependable.
and last; if you buy an AR without knowing how and when to use it, it will not defend you better than the guns you already have. If you are really concerned, get training and then decide if you need additional guns. The AR is NOT a cure all or perfect weapon for the average guy. It is a weapon best used by the well trained. At home, most of us are better off with a shotgun. Sleep well and keep the shotgun near has worked well for 150 years. Technology hasn't changed that.
p.s. being from Wyoming I'm surprised you don't own a shotgun. Growing up there, besides my .22 rifle, a shotgun was my second gun and my 30/30 was third. They can all defend the ranch. . . .