Can my husband file for divorce if has been declared incompetent?

Thank you .

I would consult an actual attorney on this. Too much to risk to go by a "crowd-sourced" answer. Attorneys know way more "tricks of the trade" that may help you. Good luck!

The answer differs by state.  I think in Florida, generally no.  A marriage or a divorce is partially a contract, and one party may not be able to enter into a contract

He probably will not be able to find a lawyer that will do this.
But you need to contact an Elder Care Attorney to protect yourself.
By the way if your Husband is a Veteran you might want to contact the Veterans Commission Assistance office to see if he qualifies for any help from the VA