First of all you DO NOT understand SOM at all if you are making this statement. There is nothing HARD about SOM. It should all feel very easy to you. It is in-between season training. Training that allows your body to recover and rejuvenate between seasons.
Your improvement will come in the fall, and sometimes during SOM for a few reasons: 1) becasue you've never done doubles before 2) because your overall aerobic development contnues another three months, and 3), if you are young, simply because your body is still maturing.
With that said, some specific advice.
Doubles. Do em. Don't think about it. Don't attempt to analyze it. Do em. 4, 5, 6 days a week. Like clockwork. Do em. 2-3 miles every day to start. Do em. Easy, medium, fast - whatever feels right to you. Do em. They say that even a broken clock is right twice a day. I got news for you, even a caesium-133 nuclear clock is right twice a day too. Do em. Like a nuclear clock. Twice a day.
Mileage. You've written down on paper twelve weeks ahead exactly how much you are going to do. Shit, you don't know what will happen twelve minutes in the future, how do you know what will be in twelve weeks?
Written goals should be vague and fuzzy, becasue that is exactly what is known about the future. Your body doen't know the difference between 45 and 50, or 65 and 70, or 90 and 100.
Take Master Po's sage advice: "Grasshopper, not chase miles. Let miles chase Grasshopper."
Q: Go over that again?
A: (1) twice-a-day, as many days as you can - four, five or six days a week
(2) increase your mileage, look, you guys are made of the same muscle and bone as me, you can do it. Find your own sweet spot
(3) meet with a group twice a week
(4) one tempo run of just four to six miles and
(5) one workout of 1200m to 2000m repeats OR 16 to 24 by 150m to 300m
(5) don't try to impress anyone, run within yourself
(6) relax, the real training doesn't begin until September
My recommnedations for you:
Tues 3-4 mile tempo run
Fri 10-16 x 150-300m (read that as “10 x 300s, up to 16 x 150s)
Tues 3-4 mile tempo run
Fri 12 x 400, or 8x600, or 6x800, or 5x1000, or 4x1200
Sample paces:
Shorter repeats aka neuromuscular training
16 x 150 accel 50, sprint 50, stride 50
12 x 200 accel 100m, sprint 50, stride 50
10 x 300 accel 100m, sprint 100m. stride 100m
Full recovery between each. slow jog or walk if you have to. The objective here is to work on the mechanics of running fast and to hit close to top end, then stride out to the finish. It's OK for you to run these hard enough that you feel a good buzz after the session. Again, you are trying to teach your body how to sprint, and by extension, to run faster.
Longer repeats. I don’t think that your PRs justify running long repeats in the 1200-2000 range. I think you would be better served by running shorter repeats at a little faster than tempo pace. Adjust your rest to 60s between. Maybe a minute on the 1000s and 1200s.
12 x 400
8 x 600
6 x 800
5 x 1000
4 x 1200
Run them at a little faster than your tempo pace, I'd say about 6:00 pace. In fact, I'd urge you to run 12x400 the first day at 6:00 pace with 60-75s rest on the first session just to get your bearings straight. If it doesn't feel easy you are running too hard. Don't be in a hurry to run fast. You have a long Summer just maintain, rejuvenate and enjoy your Summer.
Heck, you could even do repeat 200s at 40-42s and that would be a fine substitution too.
Tempo Runs:
3-4 miles at 6:15—6:30, whatever feels comfortably hard.
“My team never does tempos, but last summer i ran 4 miles in 24 minutes as a run”
I really don’t know what this means. It could be much harder than what a tempo run should be. With an 18:05 PR at 3k I think your 4 mile run is more of a race?