Personally I don't test for mag unless I'm looking for an issue. Your mag seems to be an acceptable level for the time being. I'd forget about it for now and retest a few weeks down the road just to make sure. Certainly don't chase a number though. I've had corals do great at 1200 mag and I've had mag that tests above most test kit charts. If you're dosing AFR I wouldn't think about it but every once and a while.
For the time being, work on slowly getting that Alk up. 7dkh certainly won't kill anything, so slow and steady wins the race. Personally from here, you know your dose is slowly raising your dkh, so I'd keep at the dosing and water changes but only test once a week. Once you get to your desired level, lower your dose until you no longer see that number increase. Dialing in your dose takes a long time and constant tweaking overtime as coral growth rate changes. My approach is to use a doser to dose the bulk of my alk. My goal is to keep my alk within .5 dkh of my set target. If I'm off a little bit, I don't panic I just make a small adjustment towards the direction I want to be in. On my once a week testing, if I find my dkh lower than I like, I may bump up my doser by a few mL and dose the missing amount by hand. If I test and find I overshot my target, I lower the dosed amount by a few mL and wait a week to see what the tank is doing. My point is, as long as you're in a generally stable and accepted range, your corals will be fine and continue to grow. The more practice you get at it, the easier it becomes to dial it in. After a few weeks, I generally didn't need to make adjustments on the doser but once every 4-6 weeks as coral growth increased alk uptake.
