Is there a legal way in Florida to gain visitation rights for my Father?

Well, if she has POA for him and/or he will agree to anything she says, you may be stuck. It sounds malicious but not illegal. The only avenue I can think of is if his care is bad enough to get APS involved and he cannot get the medical care he needs where he has been moved to. If he is competent and his own guardian though he can decide to let you in or answer the phone when she is not there, unless she has gotten a restraining order.

He made his choice when he married her, and the wife has first rights over any other relative. So sad you could not find common ground, but this seems to happen frequently when the spouse remarries. Try small gestures. I sent flowers on holidays and asked nothing more. Eventually the wife softened her position and allowed visits on Christmas.