Will the deceased child feel lonely in Paradise and miss his family, and was the elderly man he saw before his death Prophet Ibrahim (peace be upon him)?

Rejoice in the reward of the patient, for your child is among the "da'amees" (children) of Paradise. Do not worry about him in his grave, for he has met Allah, the Most Merciful of the merciful, and he is enveloped in Allah's grace and mercy. The children of Muslims are indeed among the people of Paradise.