I don't know what to do and I'm spiralling

I'm 15F. 2 years ago my father and I adopted a stray dog against my mother's wishes on the condition that we'd take care of him together. Up until simba turned 1, I used to take him on walks, I used to feed him and I used to bathe him. Basically all his responsibilities were undertaken by me.

Once he got older, he got a lot more stronger and difficult for me to manage. I can't take him on walks anymore because he pulls too hard for me to manage him and he almost got bitten by a stray dog once, I got so scared that I couldn't take him downstairs anymore after that. I will never be able to forgive him if anything happens to him. My father refuses to take him on walks saying that he's too tired from his job and stuff, he excretes in a designated area in the balcony.

Recently, my dog has gotten very aggressive. He has bitten my little brother and I a few times for seemingly no reason. I understand that this is because of his pent up frustration and I feel so helpless because there's nothing I can do. My parents are planning to leave him on the streets. I can't live without my baby, I'll die without him. What do I do?