I like a number of those suggestions. I am mostly indifferent to the specific bullet as long as it is not a lightweight round. Some kind of solids are probably best and in the 147 or 158 grain variety although I would not gainsay a top quality hollow point, either. The concept of snakeshot is good but the problem is that if you are concerned about serious threats you probably don't want two rounds of snake shot coming up before the hard bullets are available. If the Colorado mountains don't have dangerous snakes (I have no idea) then it is a moot issue. But, if that's a concern, some smaller gun with snakeshot might be useful if your dress, strength, and equipment package permit that.
Different rounds in a specified order only works when you know what is coming. If you do not know, which is obviously the case, six rounds of heavy hitting .357 that are all the same will be just fine. I would not discount lions and bears - I don't know what part of the woods you are going to be in but in my experience in northwest Colorado lions and bears are far more common than moose.
I personally like your choice of sixgun. A 4" .357 Magnum has always been my choice for the bear woods (so many bear threads, so little time

) whether it is a K, L, or N frame, or similar Ruger, for example (Ns are a little much in the weight department for trudging in the woods but they are excellent for the situations we are referring to).
Never forget that knife..........!