Ethanol degrades. I'd run the E85 down as low as possible, put in the recommended amount of Sta-bil (I think 4 oz?), and fill the tank with normal gasoline. When you get back, that tank of gas will run poorly, but after that's gone and you refill it it'll be good to go.
I left mine on a
battery tender for six months with no starting the entire time and it started right up the first time when I got back. I'm about to do it again. This requires that your car is left somewhere where people won't fuck with it and you have a power receptacle, so probably indoors. Make sure you make it real obvious that the tender is on there, so you don't forget it after nine months and then forget to take it off.
I didn't do anything special for the tires and I had no issues after 6 months. Anecdotal evidence only.