How do I cope with things?

You should definitely talk to your dad about this. YOU deserve happiness, too. Maybe you could ask your dad for private music lessons? Music is a great distraction and coping mechanism. He really shouldn't deny you that, it's not like you're asking for something unreasonable. As for the grades, I went through the same thing. You'll regret letting this situation get in the way of your studies when you're older, but it's not too late. Try to focus and apply yourself. Getting good grades could make you feel better too. Don't let anyone bring you down, take charge of your own life. And always try to make the best of situations, you never know what good can come out of them.