The effuent runs between 6.5 and 6.8 typically, reefkeeps. To raise the pH of the effluent, you can have it pour through more of the ARM product, as it will burn off any excess CO2 coming out of the reactor.
Many people run a Calcium Reactor and drip Kalkwasser as well. If I end up dripping kalk myself, it will be controlled to simply drip - not replace top off water.
You mentioned you're adding 4g of kalkwasser a day. That sounds like a lot to me, but maybe your tank has a heavy bioload. How much kalk powder do you add per gallon of RO/DI?
What does the surface of your tank look like? Clean, sparkling, and ripping? Smooth and calm? Oily patches here and there? Surely you are running a sump, correct? Water pouring over the overflows mixes with air and dumps into the sump should help keep the oxygen levels pretty good.
Some people have fresh air going into skimmer to raise pH. In my case, I'd have to connect some PVC in the attic going out to the eaves, and possibly a pump to push outdoor air into the PVC. Then I could attach the venturi hoses from the Euro-Reef to the PVC. It just isn't an ideal option at this point.