The Landlord can do it IF it is written into the lease agreement properly and they can remove the items without disturbing the peace.

Because of its location, I cannot have two proper units, but can have a main unit and an ADU or rent as one house (although I'm hoping the new development will bring a change to my zoning code) The basement has 8ft ceilings and is completely finished but I'm thinking of digging down behind the rear wall to add a full bedroom and reconfiguring the floor plan to accommodate another room, kitchen, and door to walkout (2 bed/1bath unit).

It also states that there is a $500 "re-rent fee" charged to all tenants who have not completed their full term, or who do not give proper 30 days notice.

What are the proper steps to take?

If you proceed with caution and screen potential tenants properly, then this should help in the long run.

If this is your first investment I would not recommend going through a wholesaler or an off market because like @Lucia Rushton mentioned you will not be properly represented in your transaction. 

Hiring a historic consultant would have paid for itself, doing proper work from day 1; funds for this expert must be in the budget.

This has been an ongoing issue since the beginning and I'm learning the hard way to screen tenants properly.

What is the proper way to market and assign your contract legally in Florida?

If you spoke to a CPA and didn't get a proper answer is either because of one of the following1) You got a free consultation and they didn't go into the details as that is out of the scope of a free consultation2) You chose a wrong CPA to work withAn appraisal that shows a higher value than what was paid(basis) has no impact on what the new basis is as a result of divorce / transfer.The fact that the property is currently rented means that there must be a basis calculated for determining depreciation.