Lizgirl, if you have dietary restrictions the one thing you have to do is stay away from the convenience and pre-prepared foods. All of them are loaded wth things those on restricted diets shouldn't have.
Sodium and sugar being the two biggies.
As you noticed, even frozen fries are loaded with salt. And they put sugar (in the form of high-fructose corn syrup) into virtually everything that comes in cans.
Something else to consider: People with health-related restrictions are most often sensitive to preservatives and other chemicals. And that's what you find in those items too. Indeed, very often we find that reactions to certain foodstuffs actually are reactions to those additives.
All in all, you're much better off making everything from scratch, so that you know exactly what goes into the things you eat.