If I understood the timeline correctly, in the beginning of the film George was being bullied by Biff and Lorraine was fat and depressed. So Marty gets a call to Doc Brown and then the Lybians kill everybody and Marty goes back in time then back to the present
Here's my question: according to the updated timeline when new Marty travels to the present (but the engine stalls), you have UPDATED MARTY from a timeline where George writes Sci Fi and Lorraine is fit and not depressed, and Marty's sister is a whore and his brother works at the office.
So what happened prior to doc brown being killed in this reality? Did everything happen the same way as it did at the start of the film (Marty failed his audition, Jennifer's father is a cock block)? Marty was shown the truck later, so were they delivering the truck to the McFly residence?
I find it odd to watch the same scene with two different sets of contexts - one with Marty who doesn't look up to his father and the other where he should be looking up to his father, but we don't get to see the revised reality.
Furthermore did Doc Brown die in the first timeline or was he wearing the bulletproof vest all along? According to BTTF 2 there are multiple timelines, but you can never go back to the old ones, so I find it easier to just imagine one timeline that gets overwritten over and over (this is why Marty disappears even though his timeline is separate from the one where he kisses his mother)