Start dosing with kent tech m. Make sure you get a test kit though. You want to keep your mag up above 16600 for over two to three weeks. This will melt away your briopsis.
I have noticed with most equipment, always go with the one that is double the rated volume of your tank. Just seems not to over work the piece equipment.
Most likely in 24 hrs would give you a good idea of how much is being added. On my 155g and 180g with 30g sump every capful of esv bionic alk gave me a result of aprox .5 dkh. And like others have stated raise it up slowly. Possibly a capful a day and check. You will also have to figure out how...
Not starting the age old argument about salts. But if you do stick with coralife you will have to dose often to keep your parameters where they should be. This is why I stopped using it because dosing was becoming a pita. I went with a salt that gives me a higher alk and use the ca reactor to...
I would recommend something like a "majano wand/stick" . If you are good at diy things it is easy to make. I made one and I feel like it has better result then aptasia x etc. It is more pinpoint and you dint have to turn off the flow. If you are interested in making one pm me.
I usd coralife salt for years and honestly it's great for fowlr tanks but not reefs.
I could not get the alk high enough either so I would switch like the others previously stated. Esv or aqua vitro is what I recommend. As far as mag I would dose a cap full of tech m once a week.
With triggerman on the cyano. Not a bad case of cyano but definitely a low flow spot. Every tank I have seen there is always one spot of cyano somewhere.
On the zoa frag possibly a montipora encrusting coral. Are the polyps coming out of it relatively round.