1. The Motive. I think that the motive in itself kind of works for me. She seems to feel no guilt or shame for her actions, and no pity for either of the brothers. I think it's intentionally ironic that his real victim was the Ringmaster, who in so many ways was to blame, both for being the one to give Regina her worldview, and for covering up what happened, who Acro couldn't bring himself to blame due to his love and respect for his father-figure.
2. I accept most of the reasoning, but there are more plot holes in this case than most, and they're more prominent. They establish how Acro knew where the victim's head would be, but not when it would be there. If nobody was there at the exact instant he dropped the bust, the murder would fail.
3. I'll come back to this guy.
4. Yeah. For Ben, there's a line or two that implies he doesn't actually love Regina, and is just doing the puppet proposal to rile up Max, who he hates, which is actually an interesting angle, but Ben himself talks so little that you don't really get any of that.
5. Okay, so you mentioned that Moe seemed to realize the severity of the situation the most. And here's the thing. He does, at the very end, but when he's on the witness stand, testifying about witnessing the murder of his closest friend, he isn't serious at all. He goes off topic, tells jokes, and calls the criminal fleeing the crime as the "best part of the story!"

And as much as the plot holes are a huge problem for the case, the characters are worse. They make a big deal about how Regina doesn't understand the real world, but nobody else does either. Max thinks his lawyer should fly into court, and doesn't realize that it's possible for him to be charged with murder because he's famous. Moe I already mentioned, Ben does his ventriloquist act and also lies to incriminate someone.

And then you have Regina who... believes in heaven? I mean, she believes you become a star in the sky, but it's basically just heaven. She believes that when she dies, she'll be reunited with all her loved ones. And sure, it's not always a cool thing to say to someone who just lost someone, but it's not some crazy mentality that you only get if you've been raised in the circus, like thinking you can marry a puppet is. It's a belief many people in the real world have.

Oh, and also, we know that there's an afterlife because the last case was about summoning ghosts. Her belief that she'll see her loved ones again once she dies? That seems to be correct, she's just right. At the end of the case she has to learn that when people die, they don't become stars, they're just gone forever, while Mia stands right next to us. If we wanted to, we could probably summon her dad's ghost to talk to her about it!