cruddy situation if you're in it but, now that I've been in the very same, I've found quite a few options for even less than what you've got to spend. For the last 2 months dh, myself, dd (3 y/o), and our now 1 month old (wiht me exclusively breast feeding and needing a decent amount of food), have been living on less than $50 per MONTH.
You may have to let totally healthful things slide a bit if you have to buy all of the cheap brands and options but, when you have some money again you can go back to the fancy brands or organics. heres what we've come up with.
eggs cooked one of a zillion ways
$1 packages of rice pilaf or long grain wild rice (SO YUMMY!) I'd eat those even if we had tons of money right now (tons of other flavors too)
tortillas with beans, rice mixes, and eggs (filling for dinner)
cereal (CHEAP cereal)
noodles with pasta sauce (get the dry sauce in the packets and mix with tomato paste), thrown in some frozen veggies and you've got another dinner!
the cheap version of pillsbury rolls to fill you up at dinner
cheap crackers for the munchies
pb&j or tuna sandwiches
drink some milk for a more filling liquid with some callories
lots of water before and during meals so you aren't so hungry
frozen veggies instead of fresh (so you don't waste money with them going bad and can spread them out over more days)
pancake mix for waffles, muffins, pancakes. see if you already have ingredients for these things.
and lots of bread for sandwiches, an empty stomach snack, toast, buttered with cinnamon, etc.
tortillas with butter and cinnamon microwaved are yummy too.
basically get the staples: bread, butter, milk, cereal, rice, noodles, tomato sauce, fresh fruit in season, frozen veggies, beans, oatmeal, some dry sauce mixes, peanut butter or tuna for sandwiches (which ever you prefer), and creativity!
after the first week it's not so bad, I promise