I'm probably not much help on breakfast. I have a short (6 mile) commute and I typically have two eggs, poached, on whole grain toast. Food seldom bothers me on the bike even on long rides. Mid-morning on ride days I might have a granola bar if I'm starving.

As for a rear rack, you might be able to use a seatpost rack with a trunk bag. I keep a spare pair of work shoes at work and everything else comes along with me. In summer I have excess capacity but in winter I expand the bag and it gets stuffed pretty full for the ride home. I think these are usually rated to 25 lbs, but the limfac is really the seatpost.