Maya outburst does not seem something unique, that is her true face when the mask falls! we see it when she drops the pretense with the MC and is always calling him idiot and stupid on a quite regular basis (even tough some people use it a endearing term...)! Also when you choose to stay with her instead of going to the party her outburst of happiness is another such reaction, the last one is her childish way when she says "look its all in" in the outdoor sex thing!
i suspect her fathers scar was a Maya gift, now when someone is under great stress, the impulse control tends to fail so her slapping Quinn makes sense! you can only press the spring so hard until it bolts!
and yes when she shows the graduation party final photo her dad did not have a face scar it also shows that even though she was the best student graduating that year, her father is not showing her any love so the Josy cat(or pussy?) is already out of the bag!
But she is growing (i do not mean on me) and asking for help is the 1st step on that growth but, if she stays just at that step it means nothing, she needs to take on more responsibility instead of taking others people shit, get a job even if its flipping burgers but until i see her taking that step the damsel in distress trope remains.
She is young attractive and extremely smart(cum laude) there is nothing stopping her from coming into her own except her own stupidity, and i still do not see it! Her plan was naive only if you believe her to be dumb she had to know there was something for the free tuition, she is just pretending that there would not be any "quid pro quo" as an excuse and plausible deniability!
basically her true face is childish and naive, her social mask is a manipulative cunt! Although an honest one cause she keeps warning the MC that her Social Mask is not her, she pretends to be a fun carefree person and the MC believes her... that is why she keeps warning him by calling him stupid because she believes anyone that believes her bullshit is stupid...
As for Magnar it does not show properly but he is probably the 2nd tallest dude in school and probably the 2nd biggest until Caleb arrived which relegates him into the 3rd on both categories since Anthony is the tallest Chad is the bulkiest and Caleb is fighting them both for those positions! Meaning that he is no push over if you add in that he has brains Magnar is a formidable foe and people should fear being on his bad side!