Re: DS isn't getting math
Just keep trying. We did pizza for subtraction and for fractions. I found $ helps with subtraction. (When DS was little I let him shop at the Dollar tree ... it's easier math.)
I liked to use "real" objects first and then write it on paper. We also did lots of cooking. (like baking cookies helps with adding. ) You might try having him set the table. Counting out how many forks are needed or simple practical applications. If Subtraction is stressing him out, focus on addition and counting and try again later.