<human>: Can you condense the text into a few key points?

I posted not too long ago looking for recovery advice between to half marathons I was running in only 7 days apart.
The races went pretty well and I only ran a few times since the last race (17 sep). I figured since it had been more than a week I could resume my typical runs which are typically 5 miles and up...Apparently I was wrong. 2 miles into a 5miler the area around my left knee (mostly on the back leftward side) was in the worst pain I've ever experienced running. I could barely go up and down stairs and I'm still feeling some residual pain.
My marathon is mid November and I really don't want to lose anymore progress. What should/can I do to keep my cardiovascular endurance up and not lose to much strength in my legs.
<bot>: the area around my knee hurts super bad and keeping me from running. What should I do to stay in shape before a November marathon?