Before I begin, just remember, we're trying to help you here- all advice takes time out of our busy days, but we do it because we want you to succeed. Just keep that in mind
I'm not sure what is going on with your salt mix or water, but I think you might have some confusion about live rock. The terms can be confusing, so this is completely understandable! For starters, new dry rock is often quarried, man made, or treated with a substance to remove the organics (e.g. bleach). All of these verisons of dry rock have very few organics.
Live rock is rock that is currently harboring nitrifying bacteria and other organisms. Dry rock can become live rock, but when live rock dies/is dried out, it is no longer the same as the new dry rock mentioned above. This is dried live rock. I'll admit the phrasing is difficult, but the concept is pretty easy to understand.
If you start with a dry rock that is devoid of life, you simply need to add life back to the rock. If you start with a dry rock that was previously full of life, you need to remove all the death.
To better understand why we are talking about curing, imagine you had a quantity of dry rocks without any organics, and when you started your tank, you dumped in a bunch of dead, desiccated fish. Clearly starting a reef tank while waiting for the fish to finish rotting isn't ideal. Inside/on the outside of the rock is the equivalent of dead/desiccated fish (in this case, dead mollusks, sponges, worms, bacteria, pods, etc.)
Lastly, marine pure is a biological media that can host nitrifying bacteria. It is confusing when people describe using a certain percentage of marine pure as an equivalent to live rock, but they are not aquascaping with it or putting it in their display tank. It is in it's own category, similar to ceramic media, bioballs, etc.