Need help from the marathoners

Sorry to hear about your DNF, I know they are always really disappointing.

But there is nothing really that you can do in the last two weeks that would make any significant physiological differences to prepare you for a full stand alone.  If anything, there are plenty of things you can do to screw yourself up!  Like a 20 this weekend.  Your longest during IM training was 17.  Your biggest month was 126.  That's barely 30 a week.  Even the simplest marathon plans have you peaking at over 40.

My advice?  Channel the frustration in another way.  If you want to run the full in two weeks, then I would just try and get in a 3 - 5 mile run every day for at least 6 days of the week.  Easy to moderate paced just to keep the legs active.  I would not try to cram in a long run as it will do absolutely nothing for you.  Then go into the race knowing you are underpepared and just take what the day brings.

I've run a marathon on little to no marathon training and nothing longer than a 14 miler (last year after IMLP) but I also average in the 1300 - 1400 miles a year range usually.