Is this person a charlatan who uses jinn, or should he be believed and the newborn named Adam, or should everything he said be cast aside, and can Allah inform some of His servants of some unseen matters?

There is no harm in naming someone Adam. As for the person mentioned who relates matters of the unseen, he is accused of charlatanry and should not be believed, keeping in mind that Allah may inform some of His servants of the unseen through inspiration or visions, and that soothsayers and astrologers relate matters of the unseen through devils.