Hi Charles Lee,
1) Are these all the tables and references to those users that I need to clean up? Or are there others?
The tables you listed sore data for the users. telerik_Roles only contains information about the roles.
2) Can I safely delete the rows from the table using the script above?
The script will delete all users with ID that does not have reference to any of the other tables. I would like to suggest using the API instead of working with SQL scripts. You can use SQL script only in case there are problems that cannot be sorted with API.
3) Are there any other considerations? (e.g. Delete from tables in a certain order, etc.)
Since you are going to delete these users the order does not matter - your script is looking for missing userID in a tables.
Please backup you database before proceeding. Changes to the database are not recoverable.
the Telerik team