IMHO, if you want to speed things up, then stop using the data table, use a custom object/class and use a list/collection.
https://dzone.com/articles/reasons-move-datatables
https://www.codingblocks.net/programming/boxing-and-unboxing-7-deadly-sins/
http://lauteikkehn.blogspot.com/2012/03/datatable-vs-list.html
https://www.monitis.com/blog/improving-net-application-performance-part-14-collections/