I don't disagree with your order. Guide what you teach by what you dad needs to do and build round that. Think of the real-world tasks that he needs to do and teach those.. so, making a call and reading / responding on Whatsapp to his friends are a great place to start. Reinforce what you teach with constant repetition and introduce new things slowly.
If he has grandkids, then it's good to task them with showing him things.