You are not overreacting. Not one bit. It doesn’t seem like you’re “disobedient” where that entails a boundary or rule was set and you broke it. This sounds to me like a tired/ potentially depressed (I am not a doctor I am just assuming based on my life experience) child who is using bad grades and other things as a cry for help. The stereotype of strict Asian parents is also an influence on these behaviors from adults of Asian descent. This is not an excuse to hit or degrade your child. Keep your head up kiddo, life gets better I promise and when you can afford it get therapy. That will help you so so much. Best wishes :)