The longest I've been out solo was 23 days and I carried all my food with me and fit all my gear, food and me in a 12 foot kayak.  I seldom dehydrate meals and never carry the packaged dehydrated foods you can buy; too expensive for the unfamiliar/poor taste they provide IMO.  I also do not try to catch/clean/cook fish. 
It is hard to find single serve packaged rice and pasta dishes so I am also often carrying more than I will eat in one meal and might keep leftover dinner for breakfast the next day.  I also almost always come home with extra food; seems on a hard and hot day, I lose my appetite. 
Regarding a food drop, mid-trip:  Some boundary areas are served by outfitters who are delivering people to a jump-off point.  It would not be too hard to arrange a meeting with an outfitter who would supply food or bring your pre-packed food which you have sent ahead to them.  Easy spots to do that would be Prairie Portage, Beaver House at parking lot, edge of Q at Saganaga Lake, French Lake, Bottle Portage, etc.  I've used Anderson's, LaTourelle's and Voyageur North outfitters for tows several times and find them organized and alert enough to be able to remember your request.  ;)