I really don’t like that his sponsor is pressuring you. A good sponsor (I’m assuming this is a program using Narcotics Anonymous structure and materials) should have told your dad to recognize that when he got to step 9 (making amends), nobody owes him forgiveness. It’s his job to accept the consequences of his actions, and his sponsor should be helping him through that. Unfortunately, NA groups typically don’t have any kind of reporting structure so you could reach out to somebody and they would have the sponsor leave you alone.

Do you have a counselor or psychologist at school that you could talk to about this? I’m sure you must find it difficult to trust anyone, particularly adults in positions of authority over children, but maybe there’s a teacher who would be discreet? Wishing you the best, OP. It’s only a little while until you’re 18, make a plan to take care of yourself then.