It does my heart good to see you say that you will take your case to Samaritan House and LET THEM DECIDE whether it sounds like abuse or not. This is a healthy action - asking for help - asking for professional help. It is wise of you to be willing to let them have the information and to evaluate it themselves. Congratulations.
Don't feel bad about making the last appointment and not going. They will understand. That kind of thing happens frequently in these situations.
You could be too close to the situation to be able to objectively judge it. As you say, you'd call it abuse if it were happening to anyone else. You've been strong - very strong, but you deserve the opportunity to talk to a professional and get input from their objective viewpoint.
Please follow through with this. All your friends here are urging you. Your big brother seems to want a change for you. Your little brother seems to want to be able to help you. People are coming to your aid not because you're helpless, but because they want to help you help yourself. You are worthy of the care and concern that is being offered by so many. And you DO NOT deserve the treatment you're getting from H. NO one would. NO one.