To start with the ever helpful site:
Sports Coach provides information on coaching, exercise physiology and athletic development for sports coaches, athletes and sports science students
I do the same as you, training more for middle distance athletics, but going to have to start thinking about the Rugby season, but then again that's kind of sorted due to my friend and I's incredible plan of 4 weeks of summer intense training

.
I basically run around 2.2 miles. It's mainly uphill, and is a beast to run on. PB is around 11mins 13. I grill myself to do that and by the end there is no way I could do a workout. If your running 3 miles, I suggest you split it too this. 1 mile focus on speed. Do ten seconds sprint, recover. This will boost metabalism also and will help increase speed and endurance. The next two miles are just solid endurance and conditioning.
Your going to have to do it on the other day, as it is completely exhausting.
Running after the workout shouldn't be done for the same reason. Anaerobic respiration would just produce too much lactic acid for you to keep fresh daily if you ran shortly after weight training.
Hope this helps.