Hey man, sorry I havent replied but I have been swamped with life lol, just plain RO is great, you dont have to have DI, I cant remember exactly what it dose of the top of my head but RO water is still outstanding.
Sounds like you have low buffering capacity. I initially used sodium bicarb as a temp fix. As my tanks fully matured, I found I did not need it anymore. Just let your tank finish cycling, and feed very little.
