I’d head to my attorney as

I’d head to my attorney as fast as possible. Your work has been stolen and you may be able at the very least to obtain a “cease and desist” order if you can prove it. I grew up in a Sicilian neighborhood and subscribe to the “don’t get mad, get even” philosophy; I’d make a point of letting everyone in your video community know what has happened, and I’d certainly inform You Tube of the situation.
Also, not to put too fine a point on it, I’d never work for anyone, ever, without a contract!