Am I obligated to forgive my brother who mistreats me and harms me physically and psychologically, especially since my family sees me as the oppressor even though he initiated the abuse, and would my not speaking to him for my psychological comfort anger Allah Almighty?

What happened is a mistake on both your parts, and both of you bear responsibility. Your brother has a right over you that you show him mercy due to his young age, and you have a right over him that he respects you. We advise you to abandon the estrangement, as it is religiously forbidden. Abandonment for more than three days is prohibited except for a valid excuse. Greet him whenever you meet him and speak to him when necessary, but there is no blame upon you for changing your behavior towards him, such as refraining from joking with him and minimizing interaction with him, in order to guard against his mischief and to discipline him. The parents should advise and guide both of you, and correct whoever among you makes a mistake.