Things have been looking up. Have continued to battle frequent injuries but am finding ways to get around them. Have reduced my mileage a lot. I used to always run five days a week, but over the past two months I've only been running 2-3 times a week (max. 23 miles per week), yet I've continued to improve in speed and long run mileage. It seems like two days resting may be just as beneficial as two days training. The reason for the sharp weekly mileage reduction has been weird things going on with my left knee. Hardly any pain but "crunchiness", popping noises. My mileage reduction was an effort to avoid making it become something worse. The condition seems to be improving gradually. But the positive by-product of this pseudo-injury has been my discovery that by running less often, I may be able to avoid injury without sacrificing gains in performance.
It's also helped that I've found some nice minimalist trail shoes, the pictured New Balance MT101's. I bought them in Virginia this summer and have been really, really happy with them. Truly minimalist, light and flexible, but the plates in their soles make rock bruises unlikely when running on trails. On asphalt I've been continuing to use the great Mizuno Wave Universe 3's.
Current performance level indicators: last Sunday, 5 miles at 6:30/mile; this Sunday (today), 13 miles at 7:06/mile. With five months to go until the London Marathon, I'm still aiming for < 3 hours.