I'm not sure 1 gun will be a universal tool that you will use for everything you intend. I also will recommend the AR platform. I personally have them in several different caliber uppers ranging from .22lr thru 7.62x39.
I like the .308 but question if it is actually a necessity for 14 acres. I feel you can do just about anything you mentioned with a standard 5.56 and a decent sidearm. I'm starting to love my full size Glock 41 which is a .45ACP.
I would also absolutely pick up a Ruger 10 22 or a Henry.
For a .308 AR, DPMS makes about the least expensive of the bunch and I've seen them for about a grand+ or so.
