problem maintaining proper parameters

[Aquattro]

You could just use kalk to maintain levels, but 2 tsp /2 litre is about double what it should be. Aim for 2 tsp per 4 or 5 litres. 24/7 is fine, and unless you dump a few gallons in at once, pH won't climb too much. I'd try to rais the levels with either kent's 2 part stuff or turbo Ca and baking soda. Once the levels are where you want them, kalk should maintain it.
Your pH now is fine.