If you only run in the one pair, then you should consider at least one other pair and alternate. Keeps the wear pattern from getting too extreme on one pair before you change them. I have at least 2 pairs, roughly half a life apart so that when one pair reaches death the other pair is on half life.

Form likely does suffer as you deal with the discomfort from the ankle. Consider also whether you favour one side or the other during work and perhaps think about evening the loading a bit more.

If you are truly serious about competing in sprints, ditch the gym so you'd be running 5X/week and start slowly building mileage. My 5 runs a week would look something like:

4 easy
8 w/2x15' tempo or, if I were inclined to go to the track instead of doing tempo, 4x1200m@5K pace
4 easy
8
10-12 w/2x15' tempo

It would take quite a while to build up to that from where you are now, but if you got your running to that point, you'd be able to run a half decent half.

Another thing to think about long term would be taking a period of time and switching from doing 3xSBR and doing a run focus for 3-4 months. The Fall is often a good time for this.

However fast you are running now at 3x5 miles, I believe you would be quite shocked at how much faster you would get.

I do double up sessions am and pm on Mon - Thurs. Friday off. Often swim, bike, run, Saturday and bike, run Sunday. Usually gives me 6 runs, 4 bikes and 3 swims.