50 mpw won't be enough, probably. 17:17 for 3mi is only like 17:45 tops for a 5k, and maybe if you had progressed more in the season, 17:20. so you're talking about a 30 sec/mi improvement in a few months.
i think you should go do a 5k road race soon to get a bearing. you may be able to run 16:40s or something right now, which is certainly much better. with 2:03, you will just need mileage to get that speed to transfer up to 5k. start off at 50 mpw for a few weeks, then do 60s for the rest of the summer. if you feel like its a lot and you arent feeling good for workouts, then you are probably running too fast on easy days. you shouldnt ever run faster than 7 minute pace on easy days. it doesnt help. when you get back to school in the fall and drop your mileage to whatever your coach wants, probably about 40, you can start running faster because you'll feel fresher.
there are no secrets to running sub 16. you gotta get in the work, and 40 mpw ain't gonna cut it.