Dave makes no sense

"Marty.. what a nice name!", proceeds to name her firstborn 'Dave'. What?

Dave is the oldest brother, yet has no car. Marty has a luxury 'dream car'. WHAT?

Dave wears a suit to the office, but doesn't have a car. Marty is still in school, but has a luxury 'dream car'. WHAAT?

Dave should have enough money to buy his own car by now, the parents should've also helped him with that earlier, especially concerning he has an office job, probably necessitating a car for commuting. Yet he has no car? WHY?

Dave has a (presumably) high-paying office job, but lives with his parents. HOW?

Dave and his whole family live in the same neighbourhood, same, exact house (also, same-SIZE house) they would've lived if they were much poorer and probably a class lower. WHAT kind of sense does that make?

Dave gets angry at always being the last one to know about 'these things' (which is an odd thing to say, makes no sense, and is very unspecified - what kind of things has he been the last one to know about, and WHY would that be, since he's the oldest brother, wearing a suit to the office, so shouldn't he be on top of things more than anyone else in the family, and thus the first to know about 'these things'?), but does NOT react to the fact that the family has two cars, one of which belongs to Marty, and the other that the rest of the family apparently shares..

..why would he even be reacting like that, if he had his own car?

Why does Dave assume Marty talks about the SHARED car, when he could be talking about his OWN car? Why doesn't ANYONE wonder or point out hor weird it is that Marty simply says 'the car', without specifying which car he is talking about?

Also.. WHY THE HECK DOES DAVE NOT HAVE HIS OWN CAR AND APARTMENT/HOUSE?!

Sorry, it's just so, so nonsensical, I couldn't help but write it in caps.

Pretty much nothing about Dave makes any sense. Also, since the 'future' (present) was changed because the past was tweaked, wouldn't that make enormous Butterfly-Effect that should reach well into how and when George and Lorraine reproduced, and perhaps completely different bunch of kids, maybe different ages and so on..?

In any case, the more you think about a movie, the more you can notice things that make no sense. Wouldn't it be wonderful if there was a movie that made sense? I haven't found such a miracle as of yet, I think Unicorns during blue moon standing next to Yetis are easier to find while watching UFOs in the sky.