I think his lack of enthusiasm on seeing Chuck, Bart kicking Chuck out and planning to leave again, his lack of enthusiasm on getting his life back when it finally happened, all coupled with him saying to Chuck that because of his personal problems before the accident that it was easier to stay hidden, all combined pretty much prove that after the accident Bart really didn't try to take down his competitor. He was lying to himself because he didn't want his life back. Chuck basically called him on his bullshit right away. Chuck knew it could be done. He was almost like the adult in the situation, forcing Bart to deal with his real life.
I also don't think Bart gives a shit about Chuck in any way. Maybe it's because he's really Jack's son (if so Jack is even creepier that I already thought he was- gross he banged Blair and has sex in the same room as Chuck on repeat occasions), or maybe it's because Bart is a cold bitter asshole & terrible father. Most likely it's a combination of the two.
Dan has every reason to be worried about Blair and Chuck, considering she spends all her free time with him; although I don't believe Blair will cheat on him. However he chose to date Blair knowing full well how she feels about Chuck. He was at her wedding where it was shown on video her saying that she was in love with Chuck, in fact he was the one that leaked the video!
I realize she said once that she wasn't in love with Chuck anymore, but Dan can not seriously argue that she didn't have feelings for Chuck that he didn't know about. Not saying she should do Dan dirty, but why is he even dating her?
Serena was hilarious when she compared Dair to Brangelina, but I hope she isn't seriously angry. Blair asked her permission and was granted it by Serena. Even if that's not enough, Serena slept with Nate while he was dating Blair- taking Nate's virginity. She then later dated him. At that point Nate was not only Blair's ex but also her ex Dan's good friend. So her attitude about Blair & Dan is laughable, although not out of character in the least.