Common sense is surely the watchword here, if it's not right then don't get into heavy marathon training. I've been through all this over the last couple of years, a sub 2:40 marathon runner well in my mid-40's, then suffered a meniscus tear on the inside of the knee, post-op was very sore, swollen and stiff around the knee. Took 3 months post-surgery to get near full movement back, but still not full strength or stability around the joint, 6 months on I still couldn't run more than 3 times a week for no more than 30 minutes and was stuck around 42 mins for 10km, then the knee went again. 9 months on from that I've had a second surgery, feels remarkably good just a week later (same knee, same surgeon) but I've learnt my lesson - I ran when my knee was clearly not 100% and with hindsight wasn't ready for running on, as a result it probably led to the second tear and I'm highly unlikely to be able to ever run seriously again - no race is worth risking that for, so take your time, get fit slowly and carefully and don't blow your future running career by being impatient. If it hurts think really hard about risking training through it, it's not like a minor muscle injury that may ease up with exercise.
I understand your disappointment at missing a big race, but believe me the prospect of never ever running again is a lot worse.
I really hope you make a full recovery, but don't set any arbitrary deadlines, let things heal in their own time - I didn't and I've paid fot it.