The answers to the multiple questions you have posted depend on the wording of your lease. You should consult an experienced landlord tenant lawyer in your area. Your lawyer can review your lease and advise you on the best way to proceed.
Disclaimer: This answer is provided for informational purposes only, does not constitute legal advice, and does not create an attorney-client relationship. Actual legal advice can only be provided after completing a comprehensive consultation in which all of the relevant facts are discussed and reviewed.
Florida Statute 83.53 provides what is required by the landlord prior to entry. There are limited exceptions to notice prior to entry listed in this same Statute. However, the normal procedure is for the landlord to provide you with reasonable notice. Reasonable notice is defined to be 12-hours notice prior to entry. The time periods for entry are considered reasonable between the hours of 7:30 a.m. and 8:00 p.m.
In the letter you refer to that was left on your counter, I presume it had language that the landlord intended to start showing the property to prospective buyers. She should not have entered the property to drop off the letter unless she believed one of the exemptions applied; which I don't see how any of them could. Moving past that, the entry seems isolated and would not afford you any damages to prevail upon unless there is more to your story that you have not provided. Going forward, the landlord has the right to show the property as long as you have been given the proper notice.
Reducing a tenant's rent and providing other concessions for the aggrevation of having people see the property is proper and the landlord should hold up her end of the deal.
Probably not as your lease likely contains terms that allow the landlord to enter the property for various stated reasons and even if prior notice is required you have no Real damages And this would be a nuisance to most judges- get on with your mOve and put this behind you.
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