My Father (46 M) and Me ( 22 F) got into an argument today because he needs to go to attend on a business matter tomorrow early and he forgot that I've told them that I have to attend a seminar that is a part of my clearance signing (I am a graduating student). When I first expressed that I couldn't afford to miss that seminar, he blew up on me for making up excuses even though I've showed them our department's memo regarding the matter. My sister (19 F) and my Mother (49 F) also blew up on me for not taking one for the team, and when I expressed that it is that important, my sister told me "No one takes your matters seriously because you never attend classes" when in fact, my professors kept on cancelling on us and the added past instances wherein they forced me to take an absence on a short notice because something came up regarding our business.

I burst into tears because I was feeling overwhelmed already with the amount of things that I need to accomplish for my clearance and they took it as me seeking for attention, even though I never uttered a word yet. I tried explaining to him that the clearance signing's procedures are now different compared to when he was in college but my Father was adamant that he was once a college student too, he worked on his clearance signing too and told me it doesn't start as early as now. I'm at my wit's end just because I stood my ground on not sacrificing just this once, and now he resorted to emotionally blackmailing me by threatening me to stop studying because he won't pay for my tuition and my graduation fee. I am willing to talk it out with him but he completely blocked me off by flat out ignoring my existence.

AITAH for standing my ground against him?

Edit 1: I forgot to mention that the reason why he wanted me to take an absence is for me to look after my little brother (15 M) with ASD. I was so caught up with my emotions that I forgot to write an important context, I'm sorry :(((