Hi @greedy ,
I do not mix Macros/Micros together, I use 2 separate bottles, so really no need to use Potassium Sorbate and Ascorbic Acid but if you want to do it i think 0,5gr of PS and 0,2gr of AA would suffice !!!
With 30ml doses in my tank, 500ml bottle will last about 16 days so it will...