"My estranged husband keeps threatening to break into my apartment. Is he correct when he says he will not be arrested because we are still married?"
No, your estranged husband is probably not correct when he says he will not be arrested for breaking into your home. The State of Florida recognizes that you have a domicile, and if it it's no longer his residence, then he cannot break into it. He cannot enter it without your permission even though you're technically still married. If he does break in, please call the police immediately. Even if he's already gone, they can create a police report. Also, even based on that threat, you may be able to obtain what's called a domestic violence injunction, which is a civil remedy which would prevent him from coming within 500 feet of your home, within 50 feet of your vehicle, within 500 feet of your place of business or any school that you or your children go to, or making any contact with you whatsoever. To violate that would also be a crime.