If you are still living with your parents, and your dad doesn't notice (or mention) that you are changing, then maybe you can wait to come out to him until you move out. Worst case scenario, if his reaction is anger and disapproval, seeing you on a regular basis will only compound that and will probably make your life hell as well.
On the other hand, you are 9 months into HRT. Changes to your body will become more and more apparent, and if you plan on going full-time any time soon, that will be readily apparent. Sooner or later your dad may notice, or someone might naively ask, or somehow you may be put into a situation where you have to come out to him, ready or not. So, to prepare for that, I wouldn't count on always being able to avoid coming out to him.
Like other posters recommended, tell him when he is relaxed. Maybe in the morning when he has just woken up or after a little drink of alcohol? I would also suggest coming out in a letter and not being there when he reads it. That way he can read it and react without confronting you immediately and possibly starting an escalating argument. Let your mom and brother know if you decide to take that route so at least they can be prepared for whatever comes of it.
I'm not a medical professional or anything, but it seems unlikely that someone could kill themselves by becoming angry. If you are worried, maybe you or your mom could consult with your dad's doctor, explain your situation (or your concern), and see what the doctor says.
