It’s been a while since I did the napkin math, but I thought that’s roughly what it came out to. How much time from seeding is that including? You need 2000 calories a day about, and there’s 365 days in a year, so that’s 730,000 calories per year.
PS Unless you’re near a missile silo, fallout is overhyped. Airbursts are the best way to damage light infrastructure and are pretty clean.