Is seeking forgiveness from Allah sufficient for disobeying my teacher, whom I thought was wrong, or should I also ask for forgiveness directly from my teacher?
If you disrespected or caused any harm to any one, you definitely need to seek from him to pardon you. If disobeyed your teacher because you thought that he was wrong, and you not cause him and harm or insult, then you don't need to seek forgiveness from him if you were not obliged to obey him.
Wassalam