Buddy, more power to you for stating what your goal is. So what if your goal is non-standard distance. IT is what you want to do.
I would suggest that your 55-60 per week now is fine It is my opinion that anything below 50 miles per week will hamper your performance unless you are Sebastian Coe. I think that doing some hill repeats every week from September to indoors is a good idea. Do some striders at mile pace or slightly faster afterward on the flats or slightly downhill. An early fall hill workout might be like the one that follows:
2-4 miles w-up and techinique drills (just a couple minutes of drills to loosen up)
5 x 20-25 seconds uphill at 80% effort (shuffle down) and 5 x 100m striders (at 80% effort) jog back
2-4 miles c-down and light stretching.
By December you might be doing the following hill workout with striders:
w-up and c-down the same,
5 x 40 seconds uphill at 80-85% effort, shuffle down and 5 x 150m striders at 80-85% effort, jog back.
I don't think you need to do any workouts harder than this until late January.
I would suggest you do one other faster day each week of aerobic fartlek away from the track. By October you should be able to do the following: 3 x 4 minutes at 70% effort, 3 x 2 minutes at 75% effort 3 x 1 minute at 80% effort jog a couple minutes between each rep. I don't think you need to do much more than this until January. The most, I would suggest is 4 reps of 4, 2, and 1 minutes each.
Remember that steady progress is a key to your long-term development.
Good luck! Tom