Instant ocean salt parameter

[hondas3000]

Hi everyone, I am new to reef and trying to have my tank stable and enjoy my tank but I have some question hoping for answer.

I am using instant ocean mix salt and I did a test from a fresh mix that power head and heated over night with gravity 1.025 and using the test kit salifert and this is what i get from the fresh mix

Alkalinity 3.7meq/l
calcium 400 ppm
magnesium 1170ppm

I did 10% weekly water change and here is my question with instant ocean salt is it a good parameter to keep coral? it is a mix reef so a bit of everything. Should i dose magnesium to 1200ppm to 1400ppm range?

My tank parameter right now is
alkalinity 4.22 meq/l
calcium 370ppm
magnesium 1170ppm

so should I dose calcium to bring it up to 400ppm and dose magnesium up to 1200-1400ppm range as well? and let alkalinity drop slowly to range? If I dose calcium how fast can I dose it? and what product should I use? can I use two part A and B or just calcium liquid itself. So please let me know what I should do and what I should continue doing so I don't end up killing any of my coral. Right now I just notice my majestic angel eating my zoas .