Some basic sprint drills and speed work should do the trick. When I played Rugby League, our club used to do a lot of plyometric training, that can also help your speed by developing the explosive power needed for sprinting.
Anyway, try this:
2 x 50m High knee lifts 2 x 50m Heel kicks(touch your bum with your heels)
Start the 4 runs in the pyramid however you like. 1 x 10m 100% 1 x 20m 100% 1 x 30m 100% 1 x 40m 100% Then for the second part of the pyramid, lay flat on your stomach. 1 x 30m 100% 1 x 20m 100% 1 x 10m 100%
For more of an endurace speed session: Perform the speed drills as before, then: 1 x 100m 100% 1 x 150m 100% 1 x 200m 100% 1 x 400m 75% Before doing the last 3 runs in this pyramid - mark out 10m on the grass, then do 5x reps of the following- jog 10m, roll a the 10m mark, get up and sprint back 100%. Then back down the pyramid. 1 x 400m 100% 1 x 200m 100% 1 x 150m 100% 1 x 100m 100%
The second endurance speed session is very tough, but believe me, that helped me alot. We used to do the middle section wich tackle bags instead of rolling, so you could incorperate that into your workout depending upon your equipment.
The best way I learnt how to control my breathing when I started running was like this - Went to my local gym, swam 10 - 15 lengths to get the blood pumping & to get my heart rate up - I then undertook a controlled breathing exercise underwater by holding my breath for 15 secs, coming up for one gasp of air then back down again. I started off doing this for about 5 mins and I do 45 sec intervals now for anything up to 9 mins. It just teaches you how to control your breathing and it helped me alot with my breathing technique whilst running.
I'd run your intervals at about 5k pace to be honest.
From your 10k time I guessed you run around 19m for 5k, maybe a bit quicker. I'd run your 1200m reps at about 90 sec laps (4:30 mins for the rep) give or take a few seconds. I'd cut your recoveries down to about 200m instead of the 400m and just jog it in about 1:30 mins - 2:00 mins.
I've always found in the past that doing the same session once a week over a month works well. First 2 sessions I do everything the same, 3rd I reduce the rest & 4th I run each rep quicker. It all depends on what I'm training for.