So I think the best advice was already given -- slow it down. Let the tank even itself out in its early days.
Whatever the parameter you are concerned about, it is not the actual *value* that is of primary concern. The *change* in value is the primary concern. We acclimate our new friends to avoid exposing the livestock to an abrupt change in water params. Doing 50% water changes can bring about rapid changes to the tanks chemistry -- and that is not good. The only time I'd do 50% on my tank is if I know something big went awry (e.g. I overdosed something or a 12" anemone died and is about to nuke the tank). I consider dropping nitrates by (in theory) 50% in one water change to be stressful on the livestock (even if temp and pH were EXACTLY matched).
I'd rather do more frequent 10% changes than an abrupt 50% change.
I wouldn't stress about nitrates. First, on the health of the livestock. Nitrates affect invertebrates (ahem...snails) before fish. At about 100 pm, fish start being obviously affected and start getting sluggish and pumping their gills rapidly.
The practical reason that we all do all sorts of crazy things to reduce N and P is because we all want algae free tanks. Now it looks like you haven't had a bloom...yet. I'd be surprised if you escape this without an algae problem.
What do you do? Well, if you haven't started with with a nutrient removal system, start one. Do whatever is easiest for you: Dosing a carbon source. Chaeto. Grow Xenia. Algae scrubber. Anaerobic reactors. Etc. There are some fancy new nitrate absorption resins available that come at a price. Everyone here has their favorite method (and its their favorite because it works for their tank).
Don't worry about the pH just yet. That will settle in over time.