Fishless Cycle Help

It is not a good idea to do 100% water change. The beneficial bacteria require to stay wet in order to survive. Being out of water for more than a few minutes will kill them and crash the cycle. I'd rather do several large partial water change than a single 100% water change.

Since you use RO water, what is the hardness and PH you aim for after you rebuffer it?
After you get fish, you have to be very careful to make sure you get the same number every time. Fish do not like sudden change in water hardness and PH. It can shock and kill them.