Hello,
To answer your first question, you can change the edit field to a dropdown menu and put the options for the menu programmatically by scanning your table for the column names. Refer to this link for more information on creating a dropdown list.
You could edit any column from the interface by directly interacting with the table by creating a uitable for the data read from excel or by using indices to access the variable data and changing it at the specific row and column.
Refer to the following links to know more about editing values from the table and also creating an uitable
