If you really want to breed RETF and are serious about it, you should really stop trying right now and begin to research about it. If you didn't even know about the need to cycle them before trying to breed, you can not have read a single article about it. There are not a single care sheet out there (that brings up breeding) that does not state that you need to cycle them. Read, read and read before trying anything and make sure you have everything you need (both supply and knowledge-wise). That's the best advice I can give you.

and how dry can it get before they stress out?
I've talked to a lot of people and got different answers, but the general idea is that 50% is dry enough.