Re: their father. I suppose there could be some embellishment or interpretation in Chuck's retelling, but I think he said it was thousands of dollars, which seems too specific to be made up. At the minimum, we know Jimmy had a hand in the store's financial troubles (so to speak), and that they were ruinous for his father. As you say, his father was naive, but I don't think that excuses joining in. Out of all the things Jimmy
or Chuck have done, this seems like the worst.
Certainly not going to defend how underhanded Chuck was in hampering Jimmy's attempts, though if you're Chuck, you really have no reason to trust him, and you can safely assume that if he knows you're behind it, he'll retaliate...which is exactly what he did when he found out. He basically destroyed Chuck's career. Would he have done it if he was upfront about it? Dunno. Hell of a chance to take, though. Either you let him in the firm and hope and pray he doesn't do what he's been doing all his life, or you tell him he can't and hope and pray he doesn't seek revenge. Lose-lose. Which is what I love about it: you can totally see why both of them are mad, and feel they're in the right.
As for Jimmy taking care of Chuck: well, that certainly does look nice, but I think it gets a little more complicated if we believe--as the show insinuates many times--that Chuck's condition is largely the result of stress about his brother, anyway.
Won't argue that he's arrogant and overbearing, but that's actually kind of my point: I think on TV shows, we tend to excuse actual misdeeds, but punish personal quirks. But if you actually add up the raw damage to society the two of them have caused, I think it's pretty hard to make the case that Chuck being kind of an a**hole is on par with Jimmy stealing from people. But the stealing is clever and interesting to watch and probably seems far removed from each of our experiences, whereas nobody likes watching an a**hole be an a**hole, and all of us know a few.