I'm trying to summon a demon on my dad
You know that's not true? Why would you choose to summon a demon?
I was possessed by him since I was born
People will not believe you if you threaten to summon a demon, but will still look down on you for trying to use it.  If you really feel like you haven't been in control of your own actions, you should talk to a doctor, since they will be able to help.
It's not really summoning a demon, it's more of soul switching.
It's cool you believe in this and more power to you, but don't you think it's best to consider how others feel about demons? Some can be super scared about it, or not believe in it at all. Why not just speak with your father instead to clear up your misunderstandings?