Is miniExtensions able to provide a form tool that allows specific users to log in with user names and passwords, and allows the person who enters the data to view and edit their entries but not see the data entered by other staff?

The answer to your questions is yes. Our portal and the form (but we'd recommend the portal) extension allow users to log in using a username and password (or just their email and receive a verification code). They'll be able to view (and edit) their entries. They will not see other users' data and they will only see data from the fields you select. You can choose which fields to share in the portal and which to keep hidden.