Food on airplane?

Looking at TSA's rules for food, there aren't restrictions on most foods that are gel-like or soupy that are under 3 oz. Would I be able to bring food purchased at a grocer, or even something like a salad in a tubawear container (with one of the unopened salad dressings that you can also purchase that is less than 3 oz.) or a sandwich or something on United airlines? Is there a limit to the amount of food you can bring (carryon)? Also, any other suggestions for food to eat on a long flight (that isn't trailmix)?