The past year has been really rough for me and I have no idea what to do.
Last year my dad started having medical issues. Out of nowhere he would start to act odd, get mad for the smallest reasons, speech slurring, buggy eyed, and would have what appeared to be a seizure. We tried to handle it but it just happened every week and would disrupt schoolwork. Every night I hear my parents yelling at each other and I just can't sleep. During school I would often run to the bathroom and cry due to all the stress I was under as these episodes are often caused by mistakes I make throughout the day. I just can't stop blaming myself as I feel like I am the cause.
My responsibilities at home grew and my class load grew to much for me and my A+ record was destroyed with me saving my grade at the at minute and bare passed with a B. This really hit me had as it is my personal belief, enforced by my relatives, that a person is remembered for their mistakes. I felt disappointed with myself and at the time I was already suffering from depression from feeling that my family and friends expected me to do well in most things.
This summer after some talking and appointments, I was diagnosed with depression and anxiety onto of my insomnia, adhd, and autism. Autism in the eyes of my relatives is a mark of failure and that you did something wrong in your past life and lead to my grandmother to spread some gossip around about how something was fundamentally wrong with me.
Anyways, during this summer things seemed to get better until my birthday. It was my sixteenth birthday a few days ago. I got some self help books from my parents along with a personalized music box. I was working on a problem out of my programming homework my mother gave my and I was getting frustrated. I did not get a wink of sleep the night before and was started to get annoyed at my misunderstanding of the problem causing an anxiety attack. My mother helped me but my dad start going on a tangent and saying stuff that muddled my understanding of the question. My mom asked him to stop and said that he was confusing me. My dad started to yell at my mom and had an episode. A few hours later, he tried to run away from home and made some choices that may as well been pointing a gun to his head. We managed to talk him down and once again it devolved into an argument. Feeling it was my fault, I started crying. This would go on for two hours and my dad had another episode.
A two days ago I found my sister about to cut herself as she had injured her hand which prevented her from being able to play her violin the only talent of hers our father would praise her on. I talked to her and found out that she has been struggling with this for the past two months. We can not afford therapy because our insurance company sucks and our many medications.
Recently I just have no idea what to do. I feel like I am taking a small problem and making it bigger than it really is. I just feel as insignificant in the grand scheme of things. If anyone has any advice I would greatly appreciate it.

First it's not your fault what's going on with your parents is between them, second if your relatives only measure you on how your grade or autism then listen here friend they have no right to so nor their sick stupid opinion on you, you are yourself not a grade not your mistakes not what you diagnosed with, none of this is you, and "that a person is remembered for their mistakes" MISTAKES ARE LESSON NOT A BAD THING A NORMAL HUMAN MAKES MISTAKES IF KINGS DO MISTAKES THEN WHY CAN'T YOU, if someone pointed any you made mistake pretend you don't hear them or piss them off by saying "Oops" and walk past them, if your relatives keep repeating your grade only say "So ?".
I don't know if I helped but at least don't look at yourself as a failure nor as grade.

Hello there! I have a friend who's been in a similar situation to yours. Especially when it came to her father. At first, she didn't want to talk to anyone about her problems but in the end she had the courage to talk to me and one consultant at our school. Whereas I couldn't giver here any decent advice, the consultant told her to try to gather her faimly and have a family meeting with the purpose of having all family members talk about their problems. At first, my friend was sceptical about the advice. But then came one day when my friend's father was in a good mood, and my friend thought that she might as well try it with the faimly meeting thing. And the outcome was a good one. Her father immediately broke down and confessed that he was going through a very difficult time, and my friend's brother, who was suicidal, opened up about that as well. After this meeting, they started to be more open to each other and instead of pushing each other down, they began to act supportive. Of course, her family still had bad days back then (this was three years ago), but she told me that her own situation, as well as her family's situation, improved drastically. As mentioned, this happened about three years ago and as we are still friends, we sometimes talk about her situation. Nowadays, her family is doing good (except that her mother lost her job due to Corona).

Of course, this may not be the solution to your problem since everyone has different circumstances. But I hope this gave you some inspiration. I really hope things will work out for you! You have my sincerest support!