My only advice would be to ask your Dad if he could just keep all of the junk food in one place, perhaps one cupboard and one drawer in the refrigerator, and not have it scattered about because you don't need to be seeing it all the time. But you can avoid one cupboard and a drawer in the refrigerator.
You can't really ask him not to eat the junk in front of you, that will be up to you to walk away from him when he's doing so. Maybe he'll get the message that way and will decide to be a little more compassionate. Sorry you're going through this, it's tough enough trying to lose weight. But I don't think he's intentionally trying to sabotage you.
Think of food as fuel for the body instead of feeding emotions