(From the trailer) A Confederate Infantryman is shown firing a Henry Rifle. These were available only to a limited number of soldiers, all Union. Even if taken from a Union soldier, the gun would be useless to a Confederate as there would be no source of ammunition.
Records show that Toby was already a slave in America by the time Kunta Kinte arrived. So Kunta and Toby could not have been the same person.
(From the trailer) when the cannon is exploding, all the gun crew are wearing wide red stripes on their trouser kegs. The stripe was only worn by sergeants. However in the scene the cannon is being tested, ALL the crew are specialist NCOs and the scene comes at the very beginning of the Civil War, before there has been much action. Hence the artillerymen are carrying no personal weapons and their uniforms are particularly clean (before the explosion) and all have red trouser stripes.
When Kunta Kinte is on the ship heading for America in 1767, the flag used has the red diagonals in the Union Jack. These we not added until the Act of Union with Ireland in 1801.