I agree that you can only seal/expunge one case through FDLE. There is a little known procedure called a clerk's expungement. I do not know if it would apply to your case. You should contact an attorney in your area to see if it is possible.
You may wish to reference the FDLE website for some other frequently asked questions. This site is very helpful: http://www.fdle.state.fl.us/Content/getdoc/7c627128-eab9-4815-bc11-4f93273f016d/Frequently-Asked-Questions.aspx#Charges_dropped_dismissed
Technically, the correct answer is yes.
Florida has what is known as Administrative Expunction under Florida Statute 943.0581. It allows a person to petition for expunction of any criminal arrest history that was a result of "arrested contrary to law or by mistake." This does not count against your one time sealing or expunction limit.
However, it is seldom used because it requires (to an extent) law enforcement's agreement that the arrest was "contrary to law or by mistake."