Hold off a few more days on the snails if you can - adding them early can actually make the algae/cyano
*worse* - (How? - if they die, then they will add to the ammonia levels and start everything all over again).
It sounds like you are *almost* there... Maybe just another day or two and your no2
count will be zero..
and algae need 2 things to grow - Light, and Nutrients (ammonia, waste materials, phos, etc...).
Set your lights on a timer (reduce maybe to just a few hours a day) and just nature take its course ----- the cyano
/algae will consume your excess nutrients, then when the tank is cycled (as long as you don't introduce new nutrients) they won't have anything to live on and they will die back.