Because he has been living there, receiving mail, and making some payments, he ulus a tenant and therefore you would have to give him written notice of eviction and follow the Florida Statutes. I would suggest you actually hire an attorney given the circumstances.
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i agree that the roommate may be a sub-tenant of yours (as you are the sub-landlord). You rent the home, then have rented out space to the roommate in exchange for the payment of the utility bills. You can issue the 3-day notice to pay or vacate and start an eviction procedure against him, however, there is the issue of the threat of physical/sexual harm.
Before making the demand to pay, I suggest immediately seeking a Protective Order to remove the roommate immediately. Threats of physical harm should never be taken lightly. You should contact a local attorney immediately to protect yourself.