The best I can figure the enclosed space protected from weather is about 45" x 69" but I think the nests eat up 13" of that so you are probably left with about a 45" x 56" usable area. I'm not a person that so rigidly adheres to magic numbers about guidelines for how much room chickens need that I get a hernia if I burp. I consider rules of thumb to be suggestions that will keep you out of trouble in most cases but not laws of nature. Most people can get by with less. Some people need more. If you follow the link in my signature below you can see some of the things I think are important.
I do not believe that chickens distinguish between coop space and run space. That's a human concept. I believe chickens are only concerned about how much room is available when they need it. They don't care where it is as long as it is available at need. If they have access to the run when they need it then it is available and can be used. If it is not available then it isn't there. That's why chickens can sleep in pretty tight quarters when it is dark at night as long as they can get away from each other when it gets light. If the run is predator safe many people leave the pop door open to facilitate this.
Your "run" space is also below the suggested guidelines of 10 square feet per chicken but many people get by with way less. Some people have trouble with even more. Quality of the space can make a big difference. Clutter to give them places to get out of line-of-sight and providing multiple feeding and watering spaces can help. If you run into a problem, feeding both in the run and in the coop might help, for example.
You are in the White Mountains of Arizona. You can get some fairly cold temperatures which, with a wind, could keep them inside. You can also get a lot of snow which can lock them inside the coop section only which would be tight. If you can wrap that run so it is always available and leave the pop door open for when they wake up you will probably be OK. It is tight but with an all-girl flock all the same aged you usually do not need that much room. It depends a lot on their individual personalities. Integration takes more room than after they have matured into a flock so I would not try to integrate any more.
As to the mice. My chickens will catch and eat mice at times but most of the time the mice are too quick and get away. Mice are really good at setting up places protected from the chickens to raise families. I do not count on my chickens to control the mice. I mainly use traps outside of the areas the chickens can get to so I can catch and eliminate mice. Since they are not poisoned I feed the dead mice back to the chickens.
I don't know why your chickens decided to sleep outside of the coop. It could be the mice, it could have been a predator scare, either real or imaginary. It could be one of them had an idea to try it. It could be mites. I just don't know. My understanding is that they are all now sleeping outside so they are not being beat up by some of the others.
My suggestion is to check them for roost mites after dark to see if that is the problem. If you want them to sleep inside, consistently lock them in the coop section after dark until they go in on their own. Just be there fairly early every morning when it starts getting light to open the pop door so they have access to outside if they need it.
Good luck!