Do some research on the relationship of calcium and alk. it seems to me that a dkh of 6 is near nsw and the calcium is way high. in the ocean I believe calcium is somewhere around 350-380 and dkh is 6-7 so you want to keep it balanced out. Again I am just going off memory here but if you look up alk and calcium in the "reef chemistry forum" here on Rc you should be able to find the correct numbers.
It will eventually all fall into place, don't try to buffer everyday and constantly correct numbers though, the tank should naturally balance out but it will take time IMO.
Also you salinity is pretty low, about what a fish only system or an old school reef would run. I try for 1.025-1.026 which is again close to natural seawater levels.
Chris