Indeed it is likely hardest for him. As an adult he'll likely have to live outside the Great Valley, though I guess he could visit it at times to visit with his friends he'll not be able to go very far into the Great Valley. Though he may patrol the area outside the Great Valley to help keep it safer for the far walkers, and adventurous kids who explore and go outside into the mysterious beyond.
Ruby may not have her family in the Great Valley, but she does know where their safety place is and though it is risky, at least till Chomper is in his teenage years, she could eventfully find them. We have no idea about Chomper's parents.