" At this point, I'd be happy with a base of 15 with a Bearikade weekender or maybe an expedition. I'm freaking horrible at figuring out how much volume food takes up."
Go to Hobby Lobby if you live near one, they sell little paper mache boxes. Buy one that is about 80-100 in3, or build yourself an exact small one out of thin wood.
Put a days food in it. Set minimum of 140+ cal/oz overall for all meals and snacks. If you stick heavily to peanut butter, olive oil, pepperoni, tortillas, precooked bacon (yum), trail mix, and junk foods, you can get 4000 cal into 80 cubic inches. Plan to eat heavily at TM, RM, VVR the first week to make up for any calorie deficit, and accept the calorie deficit you will run the last week+ to WP.
do this and you can get 8 days food in the weekender, and another day not in it when leaving MTR. 9 days food should be plenty for a light hiker to get to WP.
All food must be repackaged in ziplocks and rolled up tight. Any snack foods need wrapper pierced with needle, expel all air, then put a small piece scotch tape back over the hole if desired.