Here's to backing off and staying injury free!
ooh, damn. Things had been going so well. at least there isn't much snow, so you can ride a bike. Strengthening the legs is probably not a terrible idea.
Why bother with speedwork at all? You are already running the 10K at 8-minute pace, and that should be fine for running Boston, no? If anything, you should
continue with your endurance training, rather than focusing on speed.
And while the cat is out of the bag, it probably won't help to do any stretching for a while, but, hey, you never do that anyhow. ;-)
I am with your old friend here, +1 Fanatic.
You may not believe me, but hamstring's and lower back issues are very much connected, I find it every day in my own running.