There's a history of flooding because of the wall foundation and the back & front lack of proper landscaping. 

Wiedenmayer as I mentioned before, I'm not an attorney, but what you described does sound excessive.As a reasonable (non-attorney) person, I would "assume" that, failing to give 3 months notice, you would be responsible for 3 months rent to cover the period you should have given notice for, which could actually be less if the landlord rents it out sooner than 3 months (which, in this rental environment, I honestly think is more likely than not).There's an additional possible wrinkle that if you originally had a lease from - for example - May 2020 through May 2021 and it wasn't properly renewed into a new 1-year lease, that the lease effectively became a month-to-month rental agreement under the same terms - which would mean you actually did give the required legal notice (one full month for a month-to-month tenancy).It's complexities like that which make me think you'd be better served consulting an attorney who can give you advice based on the specific details of your lease/situation.

As much as real estate is hyper local, the proper team can be located anywhere. 

I would connect with an attorney immediately so you are going through the proper steps to get the unit producing again.

Each letter is professionaly written with proper salutation, etc.While direct mail works, it is probably the most-expensive advertising and not very efficient.

Specifically what type of permits and zoning I may need or steps I need to take in order to do this properly.

I would use the legal hotline thats available to you as member and get the proper legal advice.

If done properly, short-term rentals can offset directly against ordinary (W2, active) income without the real estate professional status.Losses generated by increasing depreciation with a cost segregation study, can be used to offset active business income without qualifying as a real estate professional.

If we end up in court will the judge see that this is in fact a "Just Cause" eviction based upon our correspondence and evidence and that I simply made a procedural error in not submitting the proper notice?

Be sure to screen properly and use this as a lesson to improve your systems.