You should be able to stop and fill up on water and snacks / food during the ride. If it's 50 or 60 out before sunrise, you don't need full gloves, and a nylon windbreaker can be rolled up and tied around your waist. I've done 70+ mile rides with just a saddle bag, some cash, some Clif bars and 2 water bottles.

If shops are infrequent on your route, I'd use a rack and a good bag. It'll be more stable and easier to use. You may also want to bring a little more repair stuff, e.g. a spare tube in addition to a patch kit. I can't imagine the aerodynamic penalty is really all that significant.

Just out of curiosity, any reason to make the 1st century unsupported, rather than supported?