Pelphrey,
I have to admit I read through your entire build thread. The best one I've seen on here so far! Your tank prompted me to pull the trigger on a Redsea reefer 350, which I will slowly get going on soon.
In regards to your struggles keeping SPS. I have not seen anyone suggest this to you.
From the beginning of my current tank I have dosed the BRS 2 part, (Calcium Chloride/Soda Ash) with 100% sustained SPS growth & survival.
Soda ash being sodium carbonate it has a slight PH raising effect. Other bottled 2 part solutions generally have a sodium bicarbonate mixture for the Alkalinity solution (less PH raising effect). Never thought anything of it until recently I ran out of the BRS product and started using ESV b-ionic 2 part. I've lost 3 acropora now since switching to ESV. The only thing I can attribute this to is the PH running slightly lower than before. So my suggestion would be try using Soda Ash.