To prevent balances from appearing on your report, you will need to figure out when each one reports to the CRA and pay it before then. Usually they report around statement date, not due date.
As for the no limit.......I believe that when there is no limit reported, FICO substitutes "high credit" for this figure. So, if your highest balance that every reported on that card was, say $5000......then $5000 would be what FICO uses for your CL. I believe this is only the case when the CC is reporting as revolving and not open.
I would take a read over on the CC forums. There are some smart folks over there that can help you out with the no limit reporting problem.