What damage could it possibly cause that their security deposit wouldn't be able to handle, worst case scenario? 

Guest Damage Insurance...This type of insurance covers small damages (no more than several thousand) that guests might do to the property.

Damage is damage.

If not, she will eventually find a new place, stop paying rent, string you along, and then move out in the middle of the night leaving you with a vacancy, past due rent and most likely a mess and damage to the unit.  

-As to rent payment, in Florida, a tenant would either owe liquidated damages (as stated in the lease or would owe rent that accrues during the lease term until such time as the landlord is able to re-rent the property on their account.

Normally, if the policy values the loss on Replacement Cost, they will initially pay the loss at the Depreciated value, once the damaged area is rebuilt, then they pay the additional amount (up to the limit on the policy).   

Looking for a rental after 13 year, he may be in a bit of shock at the rental prices, but that's his problem.As for damage deposit, you can only keep money for damages that you know he did (ie anything since 2022). 

For at least half of nearly forty years life I've lived and invested in property within a block or short walk to the beach in South Florida, Southern California, Southern Oregon and Northern Baja Mexico. 

Let them leave, repair any damages they did (from their deposit) and get it rented to the next tenant after you find out a few things. 

We think the tenant might have purposely caused damage to the unit.