My opinions about this situation has been controversial so I'll leave them out, however I will say some of the information in your abridged is incorrect and I feel like it'd be best to get everyone up to date before they release their side in a few weeks.
I'll quickly cover what you got wrong then I'll give another recap which hopefully is a bit more accurate, the information is really hard to follow and with how many liars are in the friend group, it's hard to know what exactly is truth and what isn't.
So Jackie is his Girlfriend, and the relationship was never abusive prior to the one incident that landed him in Jail.
And I have no clue how they fucked him over outside of just treating Mumkey like shit, unless that is what you mean.
Right so a bit more detailed recap.
Last Black Friday Jackie and Burger both relapsed and got drunk.
Something happened and Burger started to attack Jackie.
I forgot what exactly was said, I do know that it was said that Burger bit Jackie on the thigh though.
Jackie called Mumkey on Discord wanting him to do something so Mumkey called the Police and Burger got arrested.
The day after the incident Jackie went into her Discord VC while drunk again, and hysterically spread rumours.
Some being that Sheep/Mumkey cheated on each other before, Mumkey fucks his sister and them treating Burger like crap.
Mumkey jumped into the VC to listen to what was going on, and then made a video explaining the situation and accidentally doxxing both Jackie and Burger.
Then over the course of a few months, Burger and Jackie retaliated against Mumkey (tho Burger later than Jackie cause he was in Rehab with no access to internet for a month)
And that's about it.