If you alter the search recordset you can get errors like this. The error is telling you that you have specified columns that exist in more than one table without specifying what table the column should be coming from. You will need to qualify the name of the column with the table name first:
DataAssist is designed to work with a single table. You can alter the code after the fact like this but you may not get the desired results. If you see all the results regardless it means that you are not triggering the DataAssist Search sever behavior. On your results page it looks like the trigger is set to $_GET['Search'] so if you don't see this in the URL when you are on the results page then it is not going to trigger the new search.