Why does my dad act like this? What is the reasoning behind it?

i have a level maths paper 3 tomorrow, you'd think he'd understand that this exam only really comes once in a lifetime (unless i resit which is looking likelier every day) and how much i really want to get a decent grade in maths. keep in mind he lives with me and he only found out which subjects i'm doing around last week. he doesn't know anything about me, doesn't know my hobbies, what sports i like or even my favourite colour, anything really, i don't care about that i'm going to uni in 3 months anyway (if i even get in atp).
what is frustrating me is that every time he starts something in this house he does it in a way that makes sure everyone has to get involved. he'll be slamming doors and shouting and crashing out for two hours then be silent for the next hour then he'll go out to the pub and then come back at night, make noise in his sleep (he has nightmares so he'll either be playing loud videos on the tv (most nights), talking/wailing in his sleep (almost every night)) and then he wakes up and crashes out again. this will happen for like 5 days and then stop for a few weeks. there might be some mini ones in between, like most nights he has a nightmare but most times when he comes back from the pub he's fine majority of the time. he's broken two door handles and a door hinge already with this because he's always slamming doors and getting temperamental. every time he goes to the pub my mum is always on edge about when he gets back so i help her to clean his room everyday, no problem. keep in mind these rages / crashouts are always over something that has no solution or that we have no involvement in. he'll be mad about politics or women or something my mum has done / said. but i understand it's most likely deeper than that, tough childhood i'm assuming.
as i said, every time he starts something, he does it in a way that makes sure everyone has to get involved, which was tolerable at most all this time, but not on the week of my maths exam. i was grateful that the only other major event that happened this exam season was around the half term, but unfortunately as i predicted, on saturday, monday, tuesday and today he's been at it again. keep in mind he is my dad and i usually show him a lot of empathy but i'm not in the mood rn for it at all. i'm predicted a D/E in applied maths and i've been trying my best to get that grade up throughout the year but this week i really have been consistently trying to get my grades up and this guy has made sure that this week he has crash out after crash out day after day. he started slow on saturday but i did everything i needed to do and was able to focus and study, sunday was fine, monday he was angry at my mum but it didn't involve me too much despite it all, tuesday and today have been the worst ones and TOMORROW / TODAY (it's 12am) is my MATHS EXAM. WHY did he have to do this this week when he had the entire month to do it. he could have done it during my other exams but this guy decides to do it on my most important exam. if i don't focus and lock in i will fail. that's how important maths is because i am so bad at maths.
i can barely remember because all the days are merging into one but he had a nightmare on tuesday so was wailing in the night, that's perfectly fine and i understand that's out of his control. but that meant i slept at 1am. when he woke up (at 7am) the first thing he does is shout at my mum, he shouts at her for one whole hour straight (7am to 8am), trust my little sister didn't go to school that day because nobody was taking her or getting her ready. (i had an appointment that day and had to leave so i couldn't otherwise i would have been late). so i went to that appointment. and then when i got back he was still angry, everyone was tense and every time i heard him walk i had to try to sit really still so he wouldn't remember i was back and would leave me alone. lo and behold he enters my room and throws all of my clothes from my wardrobe onto the floor and says i should fold them. no issue, i did that. then i had to do the same for my sister and his clothes, no issue, i did that too. and i was clever enough to listen to study notes on my headphones because that was the only way i could study with him around. i was only free from around 8pm when he went out to the pub again whereas other candidates are locked in. now i only realistically had like 2 hours to study.
the next day (today, wednesday) i had an exam in the morning, then when i came back he was in a bad way again but i wasn't going to waste my time anymore because my maths exam was literally tomorrow (and is now today as i type this, it's midnight). so i took my laptop and went to the library. i studied for around 3 hours and then the library closed at 5pm and i didn't know where to go. i went home. stupidly. i got home by 6pm and left again and went to study at the nearest restaurant. my laptop was dead at this point so i looked at model solutions on my phone (but i would hardly call that studying because i wasn't understanding it) i did that for a few minutes and spent the rest of that time researching how to deal with a situation like this, i was irritated as hell at the time so idc that i wasn't locked in. i went home again at around 7pm ish. at this point my mum and my dad go out and ask me to take care of my little sister. so i give her food and make my food and all of that and leave my door wide open (to check on her) while i study. at 9pm. i studied from around 9pm to 11pm until my dad called to see if she was sleeping. i said no. and he was literally about to start raging from the phone asking if i'm serious and all of that. so i sat with my sister and helped her get to sleep and then they came back. now it's 12am and i'm typing this i just don't understand why this is happening on the day of my math exam.
like this is all extremely frustrating and if i fail this exams despite my efforts i will probably never try hard at anything ever again. it's so clear that only some people in life get to thrive and the rest of us can't. when stressful stuff happens of course the only thing i want to do is nothing. i want to watch tv and pretend it's not happening but i don't. i've still been trying to study by any means possible because i really want this grade. despite everything im still trying even though the people that contribute most to the grade boundaries have the stability to get the grades they need (and i'm not mad at anyone i just find it annoying that if i fail this my teachers will be falling over each other to say "i didn't try" or "i don't have the discipline" or "i wasted my time instead of studying". as if i don't care when i literally had to teach myself the value of education because i know it's the most foolproof way into getting out of these kinds of situations.
anyway this turned into a rant but i don't want to fail, and if i fail then i might as well have not tried at all, i could have been playing games and watching tv like my maths teacher thinks i do. just annoys me. what is the mindset behind my dad's behaviour and what can i realistically do in 12 hours.

best of luck with your exam lovely, you’re so strong and i hope it goes absolutely amazing

i kid you not this man is doing this **** again right now as i type. i only just left the house now, my exam is in less than 2 hours and he's doing this **** again. my sister is still not at school and im not taking her because i have a ******* maths exam. i dont understand why he couldnt have done this last week or even tomorrow. TODAY is my ******* maths exam and he's doing this ****. ffs i dont understand this man at all. ffs