It's pretty obvious that you have some decent speed, and the ability to beat your head against a wall long enough to get a sub 2:00 800, which isn't too shabby. I guess the real question is, what training would you respond to best? The only decent advice I can give you right now is that you should put in a long run once a week in addition to that tempo run. Bumping up mileage slowly wouldn't hurt, but if you perform well off of weight-room training, then the better thing would be maintaining consistent mileage, while following a progressive lifting plan that catapults you into your spring track season.
Can you hit 1:53 in one year, from a PR of 1:59? Maybe not. You can probably lower that PR to a solid 1:55-1:56, though, with any reasonably consistent training.
Specific advice: if you're going to a college with a reputable cross-country coach, talk to the coach ASAP and get his input on your training. Join the team, train well, religiously execute workouts with the right goal in mind, hammer out some good races. After cross country, you'll be in a lot better shape, heck, you might break 17 in a 5k, maybe even lower - who knows? Your coach should be able to help you from there.
If you're going to a college without a good coach, you'll have a harder time of it. Read, voraciously, Sebastian Coe's training model (well, more like Peter's, but whatever), and get a working knowledge of other training methods (I like Lydiard), but you're probably going to get good results from Coe. Still join the cross country team, but take your coach's training, analyze the purpose of each workout, and how it matches up with your training needs: straight-up endurance, which you'll get from long runs and mileage in general; speed-endurance, which you'll get from tempo efforts and cruise-intervals, basically any decent 5-8k race-pace repeats with short rest; and running strength, which you get partly from your mileage and tempos, and partly from hill workouts, especially uphill sprints with good rest, from weight room training like deadlifts, squats, straight-leg deadlift, etc., and from plyometrics. If you can see where you can tweak workouts to get what you need, great. Otherwise, appeal to every knowledgeable running coach or good older track athlete you've ever heard of in your life until you get the answers and guidance you need.
P.S. Make sure to get plenty of rest (both sleep, and active rest, i.e. easy runs), and eat well; especially eat enough protein. Keep training, and good luck.