If you save a submission, can it be used again for a separate filing so that information does not have to be re-entered?

No. Once you have created and saved a submission, only 2 things can occur. First, the application can be submitted, at which point it will no longer be available as a saved submission. Second, if 7 days have passed since it was originally saved, it will be deleted from the saved submission list.

USPTO FAQ - Questions and Answers (2007JUN01)