Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
If the phone will not power on/start up, there is really nothing that can be extracted from it.
Even if he could, without a password, it would be extremely limited to what he could do - in some cases, if you had a very old software version (unlikely on a model 5c) he *may* be able to access some of the photos, but even that is unlikely. Accessing messages and other content without a password ***** ***** impossible.
His threats have no merit, and (check with an attorney) you may want to mention this to the court as well that he is attempting to blackmail or coerce you. If you are really worried, you could always file a police report for stolen property, if you have any way to prove ownership of the phone and get it back from him.