I've wrestled with the suppressed PH thing for a while. I've tried running an air line directly to the skimmer from outside and that did nothing. So a couple of months ago I removed the air line and have been dosing kalk for the last couple of months. I monitor it with a Reef Factory PH meter and the kalk is slowly been increasing my PH. My PH reached 8.34 today and the low this morning was 7.98.I know you know what you're doing, and everything you mentioned looks just fine. You have a big tank, so I understand why you're running a calcium reactor. If it were me, and it isn't, I'd get rid of the reactor to raise up your PH, start dosing Kalk (especially at night with your dosing pump), and 2 part. I think you may be amazed at the results. I think there is going to be a big move away from calcium reactors in the next couple of years. I have two of them in the junk pile. Yes, they can work, but the suppressed PH is never optimal. Just my 2 cents. Wish you the best of luck. Hang in there!