LW#1: You know this is a normal fantasy, but you got freaked. Then Prudie started talking about electrodes on Alvin and the Chipmunk's nips. Say wha? I think she's trying to make you feel lucky or something.
Well, you wanted to make his fantasy come true, and it was weird for you. And to be honest, the whole "don't tell mommy" thing would put me off too, because although there is this fantasy sphere, if you're in a serious relationship with him, you are potentially a future "mommy" who is not being "told."And what aren't you being told? That "daddy" is molesting "daughter." Not that he would, but this being his ultimate sexual fantasy plants a seed. Thingies within thingies, people. I mean, why couldn't it be something simple like pirates and wenches? Or even My Little Pony? Those are so far from reality they are non-threatening.
Look, we chicks are highly conditioned to BEWARE, and for good reason. I think you and I both agree that this guy is probably not an actual pedophile. But his fantasy is one step beyond what you can really deal with, and I don't blame you a whit. It is not sexy to feel creeped out while boinking. And while you can ask him if he can put that power dynamic of powerful man/innocent naif to work in another, non-incesty scenario that works for him, if this is his bag, both of you may have a choice to make: Can you live with his scenario of choice? Can he live without it?
LW#2: It may be that your stepdaughter can take RU 486 (the abortion pill) at home, so it's not like she'd have to have a procedure that involved walking in front of her mother.
It is wonderful that your step-daughter trusts you to this degree. And while I understand your concern about your husband's not knowing, think about it this way: Have you ever entrusted some sort of information to one of your parents, begging him or her to not tell the other? Most of us have, at one point or another. And why? Because our problems and our solutions belong to *us,* not to people we don't want to include or who would trample on the decision-making.
In answer to your question: What is best for her is for you to let her make her decisions, and to not judge her, and to not pressure her in any way. What is best for her is for you to put her needs first, and to check your concerns and second thoughts at the door. What is best for her is for you to let her know you are there for her and her choices, and that you're letting her own them. What is best for her is none of her mother's or her father's business, especially as both of them sound like they have too much anger with this particular issue.
That's not to say that you can't tell her some variation of, "We both know your folks are anti-choice, and that this would be a big deal to them. That's why you're here. I feel terrible doing this as if it's behind your father's back, but I'm doing it because this isn't something he has control over. I'm not doing it because I have any control over it. I'm doing it because this is up to you, and I don't want to see anyone get in your way."
LW#3: Thumbsucking is not a good thing for an adult to do, and not just because it creates a bad impression. Her direct supervisor is not doing her any favors, and I don't expect if you tell her, "Hey, when you suck your thumb it creates a bad impression, especially around clients," that she'll up and change. But it doesn't hurt to ask. And if she's really an up and comer she'll try to break that bad habit.
I'm just going to add that Freud has some ideas about arrested development that are probably not all that inapplicable here. I wouldn't really expect a single conversation to "solve" anything. Girl has issues.
LW#4: "Look, lady, I can't be responsible for your forgetting your boots. So no." Say it in a tone of voice that says, seriously, bitch?
Then pre-emptively tell this story to all your book-clubbers, casting her as the crazy person she obviously is. But don't say she's nuts, let the others draw that conclusion. Be subtle, for Pete's sake.