How to force feed offset keyword a number calculated from table
Plan A:  Write a stored procedure to construct (via CONCAT()) the query you need, then use prepare and executed.

Plan B:  Create a temp table with an AUTO_INCREMENT column in order to number the rows.  Then look in that table for the answer.

Plan C:  Use @variables to count through the table.

Plan D:  http://www.artfulsoftware.com/infotree/queries.php#444