I recently rented a vacation home for one week. Upon my return I was notified by the landlord that he was keeping my security deposit ($450) and charging me additional money. The items he listed as reasoning for these charges are invalid and absurd. The rental was in Florida. What is the procedure I should follow to dispute these charges?

You can write them and challenge their charges.

Report them to the BBB.

And sue them in small claims court in Florida.