I was in the middle of a bad break up in February and it was agreed that I would move out of the apartment that we rented together in Florida. He verbally agrred that we would sign the roommate release form.
I moved out the last week of February and we met at the rental office the following day, at which point he stated that he didn't want to take my name off the lease because he has bad credit.
I know I can't force him to take me off the lease, but am I legally entitled to a key (he has since changed the locks) as I am still on the lease?
I simply want to force his hand so that he is as anxious for me to be off the lease as I am. No "Fatal Attraction" reenactments, I promise! He's just not the most responsible of people and I don't want to suffer because he can't pay a bill on time.

Yes, you are legally entitled to access to the apartment and him changing the locks is illegal.

Get a new key from the landlord. If the landlord refuses, call the police and tell them you were illegally evicted.

I was in the middle of a bad break up in February and it was agreed that I would move out of the apartment that we rented together in Florida. He verbally agrred that we would sign the roommate release form.
I moved out the last week of February and we met at the rental office the following day, at which point he stated that he didn't want to take my name off the lease because he has bad credit.
I know I can't force him to take me off the lease, but am I legally entitled to a key (he has since changed the locks) as I am still on the lease?
I simply want to force his hand so that he is as anxious for me to be off the lease as I am. No "Fatal Attraction" reenactments, I promise! He's just not the most responsible of people and I don't want to suffer because he can't pay a bill on time.

To many "he"s are confusing. "He" is your ex-whatever? This is the part that confuses me the most: "at which point he stated that he didn't want to take my name off the lease because he has bad credit." How is that your ex-roomate's call? If the LL agrees to release you from your obligation under the lease, that would be the end of it.