Dear Harry,
I am so happy for you, I'm glad that you have a father, and that you're living with him. You deserve to be happy. I hope that this doesn't change what school you'll be going to, or you sending Ron and I letters.
Anyways, I think that you should tell your father about you being a witch. First though, I think that you should send a letter to Dumbledore, he'll know what's best. He might even help you. I know that a witch or wizard usually comes to the homes of muggle children to explain everything to them and their parents, so if you explain everything to Dumbledore you should be fine. I hope that I get to see you sooner, and I also figured that now that you live with your dad, you might have access to a computer. If you do, I have a Skype account. This way we can talk to each other in real time, and see each other's faces. On Skype I use this name, "Hermioneee Grrrangerrr".
I hope that everything works out for you, and I hope that you like it there. Make new friends, bond with your dad, talk to you later.
-Hermione G.