[BigRunner]

Sorry for your bad day. You will get better and get back to running in THE TIME YOUR BODY NEEDS TO HEAL PROPERLY.
Unfortunately, your body is not on your timetable, it has its own.
I know you don't want to hear this, but maybe (just maybe) it's best not to put all the hope on doing that marathon. You don't need the added pressure of marathon training on top of healing after a major surgery.
That being said, if 3 weeks from now things are 1000% better, then go for it.

By the way, looking at doing St. Louis a year from now (if your not busy that weekend). I know you'll be back in top form by then.

Keep your chin up. Things will get better (they always do). I UNDERSTAND your pain of NOT running. Been there, done that.