How do I move on from my past situation under my current constraints?
Well, I think investing yourself in something like politics is a good idea, especially since there is so much to it. Maybe find some other interests too, and as for therapy, most states have a fund that you can qualify for (though if your dad is wealthy it may disqualify you
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How do I help my stepsisters with their current situation?
Honestly, I would call the cops. They are your best shot at getting help for your stepsisters. You will need them to testify to it though. Hope this helped