Originals here: http://www.slate.com/id/2267469
LW#1: Lady, you need to TELL SOMEONE. Like your husband. Any time anyone makes me feel uncomfortable, you know what I do, right after giving them the hairy eyeball? I tell my husband. It's part of our solidarity thing. And if any man, no matter what his relation to me was, spent an inordinate amount of time "tucking his shirt in" around his burgeoning boner I would first say, "My goodness, aren't you a little creeper!" and then run straight to my husband to let him know I am on troll patrol and I need his hedge clippers.
Okay, but here's the thing about your little creeper in law to be, he has probably just been sussing out your boundaries, which are inexplicably not existing. Any twerp who is frottaging on his MIL to be and exposing himself at this level to his MIL to be is not only a creep, he is probably going to escalate it.
So how do you not cause pain? Well, it's beyond that now. You kind of have to tell your daughter. And you're going to have to rephrase this in your head to, "I'm not the one who started this, HE did." This is not run-of-the mill "I think he's a nice boy but his table manners are atrocious!" or "Do you think he'll give up on his dream of being a professional wakeboarder and become a doctor someday?" This is, "Honey, you know how comfortable I am talking about sex with you, that it basically makes me want to die inside, so you have to understand that when I tell you your fiance has rubbed up against me sexually and exposed himself to me -- I think the internet calls it 'frottage' -- the last thing I want to do is share this violation with anyone. But you're thinking of marrying him, and if I didn't say something about his making his future MIL a part of his sexual whatever it is, I'd be doing you a disservice." Then, in as much detail as you can handle, recount some incidents for her ("It was Thanksgiving. I was bending over the bird, which I had just pulled out of the oven to baste. Suddenly, I felt something up against my bottom, rubbing. I turned around and it was him").
I would hasten to add to all that if you have children, when they are getting to the age where they are going to act sexual (and I don't just mean having intercourse) it's probably a good time to start a conversation about good relationships, consent, boundaries and how you are only talking about this because you want them to have a happy, healthy sex life.
LW#2: No, just don't do anything. Leave her alone. Unless you run into her in some circumstance whereby you can't get away from her (carpooling or something?), then say, "Y'know, those years ago, when I was such a huge douche to you? It's not like it helps or anything, but I was bullied myself, and it took a regrettably long time for me to actually learn from it. Being such an asswipe to you, personally, has been pretty much the thing I've carried around as the most shameful thing I've ever done, and I couldn't be more sorry for how I treated you." But if some asswipe from my past tried to tell me they had changed since middle school, I probably wouldn't be in the apology-accepted mood, unless it was done sincerely, face-to-face.
LW#3: When my friends with a timeshare can't use theirs, they offer it to their friends so long as the acceptors also pay a "maintenance fee." Then the friends don't go to the timeshare. Because if they did, they would basically be using what is theirs and charging someone else and, hey, didn't they offer other people a vacation i.e. a place that will be fun and not where other people are?
But you knew BIL was part of the vacation equation, so I'm guessing he's paying the maintenance fee, right? And at least he's flying down there on his own tab. So as long as he doesn't mind not eating out every night and you recognize that everything is cheaper in the Caribbean once you're there, maybe you might not want to pay your two-thirds of the maintenance fee because it will be about the same in the end?
On the other hand, if his being sneaky is what is making you mad (as it would me, much more so than paying for stuff), you might just have your husband ask if he can front bro some cash on the front end so it isn't "You're paying for all this stuff you can't put a value on."
LW#4: OMG no wonder you're in therapy. Just say, "I'm hoping this will be therapeutic for me to say this and an indication of progress, but you constantly misspell my name on my bill and don't seem to notice it when I send you a check with my actual name on it. OMG PLEASE DON'T HATE ME FOR SAYING THIS!!!! SOB!!!!" I'm sure she'll find a way to drill down on this for the next two years as she sends you new, accurate bills.