That poor man. It’s sounds like an impossible situation. So many grandparents are raising grandchildren. My mom practically raised my nephew. She picked him up every day and made sure he did his homework. Maybe share good videos. Many times it easier to understand something if you are alone and can concentrate. I’m a visual person and if someone starts talking about things I’m not interested in or don’t understand my mind starts wandering and I unintentionally zone them out. As someone mentioned pray, that never hurts. Hope you find a way, sounds like he needs a compassionate friend.