"Does FL require a separate license for 3 wheels like WA. does?"
FL does not require a separate license for three wheels but does have a separate "three wheel only" endorsement. The students in our S/TEP class that pass get the"three wheel only" endorsement.
I already have a "motorcycle also" endorsement on my FL DL which covers two and three wheel motorcycles.
I forgot to mention that one guy in the class is getting a new Morgan three wheeler with the SS motor so he needs the "three wheel only" endorsement on his FL DL.