Vicki hasn't reached her 'I don't understand' stupidity phrase yet but I do think she should have been more wary of going anywhere alone with David. Maybe she thought she was making progress up to this point, but even if that was true, she just undid all of that by accusing the boy of stealing the pen...so yes, she should have been more on her guard.
I honestly don't think Roger would have cared if David had done more than just frighten Vicki. It might have even given him the leverage he needed to rid himself of the son he clearly doesn't want. Elizabeth wouldn't sent David away after the bleeder valve accident since Roger survived. But with Vicki dead, Roger would not stop until he made Elizabeth see that David's latest actions have now resulted in absolute death, and that she would have to face the fact that she can't allow the boy to stay around and cause any more destruction and mayhem.
I do so like the blossoming relationship between Joe and Maggie. I wonder if Maggie always had her eye on Joe, but she doesn't strike me as the type of gal who would steal another's boyfriend. I think she does sense that Joe is starting to get fed up with Carolyn and is treading the waters by inviting Joe to dinner and explore from there.