A few things I saw reading your thread:
Comment on someone elses post. You didn't start with "real" live rock, but did start with well established live rock from tank. This rock was probably well cycled before you ever stuck it in your tank provided your LFS had some bioload before they broke it down. Good job on waiting it out though. The sponges and things that are growing on it do well in reef tanks, which is why they are growing on the LR in the first place in your LFS's tank. This is a good sign of mature rock and means you have a great start to your tank vs dry rock/sand. The comment about this stuff probably not making it in the long term is true of "real" live rock imported from the ocean, not so much of established tank live rock. Just some info for you...
Also, the "liquid" that your LFS was trying to sell you is bottled bacteria. It will help speed up your cycle in most cases, but usually used for dry rock tanks. I use it to seed my final fish QT as I don't keep one cycled. Has worked well for me although others will argue.
Also, once your cycle is complete, you can stop testing ammonia and nitrite. Once you start adding fish, you can test if you want to make sure your tank is processing it well, but unnecessary in my opinion. Also, if you are going to test pH, get a cheap meter off of amazon. They work fine as long as they are calibrated. Much more accurate and easier then API kit. I only use it for water changes to make sure my water is ready to add (I use muriatic acid to drop the alkalinity to match my tank, takes a couple days to stabilize pH) otherwise I don't test pH.
One big tip - don't strive for 0 nutrients. That's one of the surest ways I know to struggle with coral. There was a big craze of 0 nitrate, 0 phosphate to control algae, and now there are lots that struggle with coral growth/color and even survival. This is one big reason, especially on new tanks. Others have said this but,-5 nitrates is a good target, and 0.03-0.09 phos is what I like to shoot for. Get a good CUC for algae control.
Great job so far, and good luck.