Serious running issues (Page 2)

I was thinking about your problems while I was out on my ride today. Maybe the run/walk method would be something you could do to help extend the length of your runs if you really want to do an oly. While it's not something I've ever done, I have seen lots of people using it. Maybe something like 4 minutes running and 1 minute of walking would be enough to give your legs some rest before you have problems. I think people go anywhere from 2/1 to 10/1, so you may have to experiment to see what would work best.

And go back to your old model of shoe.

I agree with most of the suggestions here so far.  The only thing I thought to add was that your mileage was too low to really be in the need for two pairs of shoes for different work outs. However, you shouldn't be uncomfortable having two pairs.  It should be normal to transition from you new to your old by using your old shoes for longer runs and gradually working new shoes in to longer and longer runs so that by the time the older ones are dead you have your new shoes ready to take on the whole load.
Also having different shoes for different workouts isn't that bothersome to me.  I am a trail enthusiast so I have road shoes and trails shoes, as long as they are both fit properly you shouldn't have a problem.

I have had problems like the ones you describe.  Being in the Army and doing physical training almost 5 times a week, I have learned something about my body, but even then I am not a great runner.  I was able to smoke the hills, but lost time on the flat and downhill surfaces due to leg pain.  I tried insert, different shoes, and strengthening exercises.  They all had some effect.  The biggest problem I had was with my back.  The pain would start in my lower legs and then work its way everywhere.  It would greatly hinder how long and fast I could run.  You might want to try stretching exercises for your lower back.  Plus, add in all the other things the others have posted.  Something is bound to work.  Good luck.