No worries. I rode with a fella (for 3 or 4 days) who was on his racing bike (college cycling team) with a heaping Coraplast carton and two panniers on the back. He was just fine. Made it coast to coast. He changed his rear cassette to a more mountain friendly set and never looked back. Don't over think this.

Don't buy a lot of grub and carry it with you. Buy as you need it to avoid carrying a lot of weight. Forget about getting some org to sponsor you—unless it's your folks. Save your cash. Buy food together for the savings. You can get by on $20 a day, perhaps less, no frills.

Consult www.crazyguyonabike.com—chances are somebody has done and documented a trip that would be close to yours. In fact it's got all kinds of useful info. This forum as well. Search "touring cheaply" or something like that.