The Shenandoah wasn't a confederate privateer (a vessle in possession of a letter of marque from the CSA). It was a military cruiser paid for and commissioned into service by the Confederacy under the authority Stephen Mallory, confederate Secretary of the Navy. and that one black guy could have been a Jamaican or African.
Unlikely. The black sailor was named Edward Weeks, an indisputably anglo-saxon name. What little is known about him indicates that he was originally either a slave or servant of a fairly well to do family headed by George Canning, who was London born, and his wife, who was a North Carolinian. Later in life he was employed by Canning, who became a close friend and who died from an earlier civil war wound in Weeks' arms. Canning was a confederate when he signed on with the Shenandoah and is believed to have served at Shiloh. Weeks, who was significantly older than Canning, signed onto the crew at the same time and with equal pay at the insistence of Canning.
Again, show me, among the tens of thousands of rebel soldiers caputured, one black man.
Just did.