I would simply second what GTF stated. The main thing you could do given your goal is to drop the non-running exercise and use the time and energy you were expending on that on running. You become a better runner by running. As for workouts, you're not going to become a speed demon in the long term by pounding out intervals now. I'm sure you've studied up on periodization already. You can maximize your speed within 8-12 weeks but how how much speed that amounts to will be determined by the base you have already established.
As for specifics on what to do over the summer, it's been out there for a while but I'm still a fan of the Summer of Malmo.