First, you need a Washington State DUI Defense Attorney and with that kind of history you are not going to get a reliable answer from an online site such as this or any online site. Most DUI Defense Attorney gives free consultation and if a member of the National College for DUI Defense, will be more than happy to speak with you in their office.
In general, if the DUI was dismissed or you were found not guilty, then it likely can not be used to enhance this DUI. The other DUIs will depend on when you got them and could depend on the type of DUI it was in Florida versus what Washington State would consider a proper DUI conviction for enhancement. Each State has its own case law concerning these matters and your Attorney would need a whole lot more information than what was provided with your questions.
Assuming that the court/prosecutor knows about your Florida history, this new offense would likely be treated as a second offense within seven years for purposes of sentencing if you were to be convicted. The only cases, however, would most certainly be looked at as an aggravating factor. I have included some links below so that should help answer your question. With that being said, you really do need to speak with a DUI attorney as soon as possible. There are many considerations that you need to prepare for beyond the potential consequances if convicted.
The most immediate concern is how you will be treated at your first court appearance. If the court is aware of your history it may impose a high bail for your continued release, place you on home detention, make you wear an alcohol sensing bracelet, have you put an ignition interlock device in your car and more. A lot of this depends on where you were arrested and in which court this will be filed.
By all means continue doing your research online, but contact a DUI attorney before you go to court.
As my colleague from Washington stated, if you were found not guilty the offense it will not count for determining the minimum sentence the judge is allowed to give you. Washington considers all convictions where the incidents occurred within 7 years prior to the current incident. Non-DUIs (e.g. Vehicular Assault, DUIs amended to Reckless Driving or Negligent Driving, etc...) can also count as priors. The judge can give you up to 1 year in jail, a $5000 fine, 5 years of probation and more on any DUI conviction (even the first one). Which court you are in, and the particular facts of your case, will have a lot to do with what you can actually expect.
If convicted of a third DUI you will be looking at jail. Washington does not allow inpatient treatment in lieu of jail. However, a deferred prosecution (2 years of treatment) is an option in Washington if you haven't done one before. You should consult an attorney about all of these options.