If he recommends conditioner, then I wouldn't recommend getting there haha. Find someone who will sell you RODI water, in sure there will be a local person to help you. Keep your salinity at 1.025/1.026. Lookin good, glad we could help!!
Just extra info, I don't like to use buffers and dosing I like the natural way. My PH has always been at 7.8, picked up a mini fan and installed near my sump to provide more air flow around the sump. That worked and is keeping between 8.1 and 8.2. I have also started turning my light for my sump on during the night while the main display is off. Different times of the day will give you different PH readings, always test at the same time as previous.
Just my .02 fella