Ummmmmm...I'm also a little worried that somebody has got nitrate, and nitrite mixed up. Nitrate cards normally show you readings of 0, 5, 10, 20, 40, 100, whereas nitrite & ammonia is 0, .25, .50, 1.0 and so on. I would urge you to go back to the shop and double check the readings and make sure you know exactly what each reading is, ammonia, and nitrite, nitrate and pH. The two toxins you really have to worry about are ammonia, and nitrite. Any readings above 0 is unacceptable. Whereas small amounts of these toxins are not normally fatal in a very short space of time, they can do irreversible damage to your fish without you even knowing about it.

I would advise anyone to use test kits made by aquarium pharmaceuticals. The reason being is the ammonia solution turns green if ammonia is present in the water, nitrite is blue, and nitrate is yellow, orange and then deep red. It's very difficult to mix them up unlike tests made by tetra which are all yellow, as far as I can remember

Yes, certainly make sure not to confuse Nitrite and Nitrate.

As far as the behavior is going, that all seems pretty typical for a skiddish CA Cichlid. I didn't actually witness my Red Devil eating for a year or so. The shaking and shimmering is territorial behavior. Try observing the tank from as far away as possible. Your fish is likely very intimidated by you presence. All this will of course change over time.

Just for fun. If you can figure out where exactly in the tank this fish is trying to protect. Get on your knees and stick your nose right on the glass near that spot. You may just see this guy step up and try to fight you! That's always fun.