i don't think you need 3x/day.
i dno, here's what I would do I guess.
when will you test? early? late? whenever you test, i'd make that your "hard run". So for example, say you test in the morning, make that your hard run. Then in the evening, go at a light pace for ~30 minutes or so. I like the 2x/day approach, because in one session you would be much more specific (running harder for 1 to 1.5 miles at approximately the time you would be testing), and the other is just general relaxed cardio (burn some cals, get the heart pumping, relax & breathe).
then i'd just throw in an active rest day whenever you feel you need it.. if you feel sore/drained from doing that 2 days in a row, then just do an hour of walking with some extremely light/short (50-100 yards) runs mixed in.
for your hard session, i'd warmup real good and then run hard for 1 or 1.5 miles.. By run hard, I mean push your pace but not to the extent where you're accumulating so much lactic acid that it's making you quit. That feeling should be saved for the last sprint (~200-400m). I wouldn't look at your time while you're running either, wait until the end. after you're done with your hard run (don't stop), do one more cooldown mile at a relaxed pace.
make sure you don't do too much heavy lifting this week, that'll tap into your recovery. You'll want to focus mostly on this running stuff & bodyweight exercises/yoga like you mentioned. Also make sure you're not under-eating/under-hydrating. If all of a sudden you cut calories drastically you'll feel like even more shit when you're running.
as far as your stride, trying to make it "longer" can end up working against you. If you know for sure it makes you faster then cool, but, i've found (and read) that you should really just focus on hip extension and/or stride frequency instead. Taking shorter strides but at a higher frequency (~180 per minute) can speed up most people who aren't used to running.
hope that makes sense.
