Be hurt, be frustrated, be afraid, and feel the feelings that you have. It's normal to have those feelings, but we repress them and send them away - especially when dealing with our families.
Then those repressed feelings squirt out in interactions with other people - startling them and us sometimes by how out of proportion they are for the actual situation we're in.
Being angry at people who wrong us is normal and healthy and expressing that anger productively in a way that establishes and reinforces your boundaries is protective and appropriate. It's important for all families, for normal development, certainly, but most especially for survivors of familial sexual abuse where the family system prevents acknowledging the truth because it means shame and acknowledging their failure, and for some, their guilt.
Family dynamics resist change. If you change in a fundamental way, then others in the family are forced to change, too. Resistance to that change is very common.
Your brother doesn't want to accept responsibility for what he did to you, to avoid it, he's both denying his guilt and transferring the responsibility and impact of his actions (potentially breakup of the family) to you. This is abusive manipulation and control. You are innocent - he is guilty. Be angry.
Your father doesn't want to accept the feelings of guilt and shame that come with a parent realizing they failed to protect their child in such a fundamental way. He also doesn't want to accept that another son could be the abuser. What does that say about him? It's much easier to create a false narrative that rationalizes why the accusations can't be true, hand the narrative to the abusive son as a shield, and once again place any and all blame for the situation at your feet. It is cowardly of him. Be hurt. Be angry.
It feels to me like your love for your family and your caring for them is warring with your own need for truth around being abused and feelings of betrayal and pain at your family's reaction to that truth. Self harm is one of the things that can happen when we have a conflict that feels unresolvable (even though you always have power to act) and where everyone else's words and actions lead us to judge ourselves to be worthless. Reject those words and that conclusion.
It seems like you are still trying to take care of everyone, that you feel like the fate of everything lies on your shoulders, like everything that happens in this situation is your fault. That isn't true.
I believe you. You are blameless and you deserve to be taken care of and loved. You know what is true. Refuse to accept the lies and denial of others. Take steps to protect yourself and establish your boundaries of acceptable behavior from your family. It's your right.
You can feel angry, hurt, and betrayed by your family and still love them. That doesn't mean enabling their denial and avoidance of their responsibilities for their actions and inactions.
Everybody here's got a story to tell
Everybody's been through their own hell
There's nothing too special about getting hurt
Getting over it, that takes the work
- "Duck and Cover" by Glen Phillips