Hm... well, coming out is a deep and personal choice, but my advice: what makes you wary of this friend? I mean, has he told people stuff about you before? You could test it, like tell him something about yourself, and then ask him not to tall anyone, and see what he does. If he doesn't tell anyone, well, then he's probably trustworthy. But if you don't trust him not to tell anyone, and you don't want anyone else to know, then coming out to him might not be a great idea.
As for your family, how is your dad homophobic? Is he just mildly homophobic (i.e. "Oh, yeah, those gay people are so weird LOL!!"

or severely homophobic (i.e. "ARG!! I HATE GAY PEOPLE I HOPE THEY ALL GO TO HELL AND I NEVER WANT TO BE AROUND ONE-"

If it's the latter, then my personal suggestion would be don't come out if you don't feel safe. It might be best to come out when you've moved out of the house, or when you are away from your parents. If he's the former, then I'd ask if your home enviorment is stable? Are your parents generally loving, caring people? That's when it might be safer to come out when you're still at home... I've met many former homophobic people whose opinions change when someone they know is gay.
In the end, it biols down too: Would you be comfortable living as a gay/bi/trans/whatever individual at home? Are you comfortable with the idea, in general of coming out with your Dad living with you? Good luck. [sorry this ended pretty abruptly xD]