I use SMS iall all my tanks, all with 0 KH due to my use of only RO/DI water and never experienced any crashes or any other PH issues. My PH is prolly around a 4.7~5.1 and what most would consider scary low but all my Amanos, CRS, RCS as well as fish doing fine.

I think you are scarying youself with a really minor issue that will only last for a few months...if that long Just use it as is and you will be fine.

You might have already seen this, if not, you can see here I do inject lots of Co2 regarldless of my KH of 0. I'm not suggesting that you inject as much Co2 as I do but just trying to show you that I am doing it at a more scarier level than you are/will with no issues.