Do not add fields to the template by modifying the HTML file. Instead, edit the Form Template in Content Server to add the field, and then export the template as HTML.
When in doubt, if you are using SQL table storage, choose the Verify matching schema template and table named <table name> option in the Manage Relational Table list. This should help when you are having problems naming fields. Remember that your choice of field names is limited by the database.
When creating a view that is intended to act like a subform, do not delete the fields from the Form. Make them hidden instead.
For more information, see Edit an Exported HTML Form Example.