How do I find 1/16, are there measuring spoons for this? and I would rather dose liquid if possible, so can I just follow http://calc.petalphile.com/
and make my own macro?... I will be mixing all these three together into a 500ml solution.
Yes, there are small measuring spoons. They are sometimes called "dash, pinch and smidgen" measuring spoons.
That shouldn't cause no (sic) complications?
This will be fine.
I will stick with my chelated trace for now I think, and maybe if aquariumfertilizer ship to uk I will purchase some CSM + B and then add the Magnesium to the trace mix if in your opinion that would work better?
I would just keep the magnesium (sulfate) separate from the trace mix altogether. Just keep it with your macronutrients.
and I'm thinking maybe I should just stop the CO2 but then the plants won't use the ferts?
This could worsen your problems: fluctuating CO2 levels can often lead to additional algal problems.