Edit

I am sorry you are in this situation. It is a tough one but you can get out of it if you act fast... remember the saying, you want it done, fast, cheap, or right? Pick 2.

R3 is usually a BAD idea but at 29 it may be the only option.... you have waiting a LONG time to take your GMAT.... that's part of the mistake. You would ideally have taken it in Aug/Sept again but that's past and gone.

You can help/save your situation but it depends how desperate determined you are.
1. You probably need a consultant who could guide you through the process and applications. Your score should do for the school that have 670-680 as the average
2. If you are aiming to apply to a better school, you probably would need to hire a tutor ASAP who can point out your weaknesses/issues and get you back on your feed and hopefully closer to 700 by the 8th of Dec
3. Some schools will take a revised GMAT score as I recently learned (Stern) whereas others won't take any additional info once your application has been submitted. there is a chance.
4. You are really short on time for essays and applications, hence a recommendation for a consultant above. If you are done with essays/apps, then skip it, if not, see #5 below.
5. An admissions consultant will COST you. A consultant will be $3,500 for one school and $5K for 2. See here: price-comparison-of-mba-consultants-and-links-to-their-sites-161420.html Not only that, it will be hard to fine a free one at this time. A decent tutor will run $100-200 per hour, so that's another $1,500 or so

I would say it will run close to $8 or $9K to get it done. The good thing about 29 is that you should have more money than most 26 year olds... but that is making a number of assumptions. But if you want to get it done right and fast, that's probably one of the only ways I can think of since time is very tight.