You have to put the most limiting condition at first. You say apple, do something. You say apple cobbler, do something else. Guess what, as soon as you say apple, the first thing gets done. You have to put the most limiting condition first.
/cast [nomod] Greater Heal
/cast [mod:ctrl/alt] Dispel Magic
/cast [mod:ctrl, nomod:alt] Renew
/cast [mod:alt, nomod:ctrl] Flash Heal
/cast [mod:shift] Abolish Disease

Other things to watch out for, CTRL-1 through 9 is spoken for (already keybound), same with ALT-1,9 since that makes 1-9 cast on yourself. The idea is sometimes some keys work, but other modified keys don't, is because they are already keybound to something.

Hope that helps and good luck.