I haven't done any speedwork (please critique!)

Hammering your runs under 6min pace is not going to make you a good 800m runner. Depending on the type of person you are, being a sprint-type 400-800 guy has very different training from someone who is a 800-1500m guy.

But if your 100m is true and not some bogus split from a relay, you are probably a sprint type of guy who is still talented enough to hold on to run a 4:20 mile, especially from hammering that mileage. You really need to be on the track and doing intervals 2-3 times a week. With longer workouts of 600-1k's one day, a speed workout of 200's or 300's at a fast pace with 1:30-2min rest. and maybe hills or some other medium workout as your 3rd workout. Then have days in between be recovery runs at 6:30-7min pace. The 800 isn't an endurance event anymore in college. You have to be able to run 51 for the first 400m and hold on to be competitive on the national scene anymore for the 800m.