Yes I understand the c concern. The picture is a bit blurry, but there is not a lot of color difference between the various pH values.
I'd consider a cheap ph meter, if I were you.
If the alkalinity is steady where you want it, I would maintain the amount of limewater you are dosing now.
I'm not sure I understand the questions above. If alkalinity and calcium are OK, there is no need to change anything.