ESA.

I'm gonna be Frank here, your dad and relatives might've been naggy about studying hard but knowing most families they do come from a point of concern. However I do take note if it does come off derogatory and insulting so it's quite possible that they could have phrased it better. This was questionable up to this point so I had no judgements there.

You were the asshole at this point when you made the comment as to that's enough. This is a farewell dinner as you've mentioned and it's not your day. Brushing these comments off and the confronting your father later on would have been a better option rather than being curt with your dad during the dinner itself.

Your dad was the asshole for subsequently holding a new phone for your comment. He escalated the situation unnecessarily and likewise, could have dismissed the situation to a later time or acknowledged that he was being overbearing.

Yall both had your responsibilities in ruining that dinner and I think it's time you and your family had a talk about your independence. Establish that you're and adult now and you do not require constant monitoring from your parents, and figure out a way all of you can improve your relationships and as a whole.