I would try using EPGY math. It is a computer interface, and presents only one problem at a time in a fairly large typeface. Answers are typed in. This helps my DD immensely!
For paper calculations, try using graph paper with 1/2 inch squares and faint lines. This can help line up columns for long-division, etc.
I would have him work on the math facts daily, but NOT TIMED. It's important not to give up on this because knowing these facts will take a lot of burden off his working memory and allow him to work out more complex problems.
