If jades grandpa was dead while she was still a baby how did he find her dead dream self and have it stuffed while riding a big ship in prospit? This question has been eating me alive.

Grandpa used the portals found in the Frog temple on his island to enter the Medium sometime before he died and before the session started. Because the Medium’s timeline started when John entered, Grandpa was sort of traveling in the future. He took Jade’s dream body back through the portals to Earth and stuffed it.