Dear LW4: Yours is a tricky letter, as you really ought to be commended for going through testing before sleeping with a new partner. Please note that I avoid the biphobic trap of adding, "especially given your selection of partners of both genders". (As an aside, someone on the Prudecutorial staff did a better job than usual at suggestio falsi through suppressio veri.) The tricky part is that, as Lucy Angkatell points out in The Hollow, the answer appears to be a self-serving or enjoyable suggestion. But the solution is obvious - if women won't get tested with you, then just stick to men. The world will not end if bisexual people make the conscious choice not to indulge their capacity to take pleasure from both (or all, if one goes beyond the binary) sexes. And the men you partner don't make any sort of kerfuffle when you bring up testing.
Now, to provide a more practical suggestion than the Prudecutor, who would rather berate someone for the horrible crime of having the wrong manner than make a useful suggestion - after all, why on earth would an advice columnist ever want to make an useful suggestion? If people solved all their problems, then they might never consult advice columnists any more. (That they might develop new problems seems not to have occurred to her.) The answer is unilateral disarmament. Should you insist on sleeping with women in future, then, when a relationship progresses to the point, accompany your inital suggestion with a copy of your test results. Quite naturally, your initial suggestion is intended to precede the actual first boink, as both parties should have time to consider. Any potential partner favourably inclined will then respond in kind. This may be a bit passive-aggressive, but passive-aggressive is at least an improvement over overtly aggressive.
Dear LW3: Why do people assume that they will be able to sneak around behind someone's back and get away with it? Such short-sightedness can only be a sign of desperation. If the problem is S3, it is quite possible that they have tried to raise the difficulties his condition has given them with you, only to be shot down. Or perhaps they have observed your conduct with others and made the pre-emptive decision that you wouldn't listen or understand (much as, in the specualtions of Gladys Stern, Maria and Julia Bertram likely decided well in advance that there would be no point in opening their hearts to Sir Thomas, who would in their opinions be incapable of understanding them).
But I have a little idea that goes beyond the thought of the Prudecutor and probably most of those who will comment on the situation. I note that you mention you and your children have shared a house with families. This is a most interesting point. The mere fact that you are a single mother does not make your family any less a family than those which have the good fortune to be headed by two adults (and there are those opting to treat arrangements with more than two adults as a single family unit besides). But many people feel otherwise, and will require two parents. If you are of that persuasion, I suspect that your friends are also. And there we have the rub. You mention your two friends, but not their spouses. It is highly possible that the mother who raised the ugly truth either dislikes your not being equally friendly with her wife, or suspects you, as a single interloper, of having Designs on the poor woman. Not every couple can socialize well with a single on a permanent basis - not necessarily great, but a possibility. Or perhaps there were threesome hints you missed. If your friends are also both single parents, they might be conducting a clandestine romance, and your son was the most convenient lie available. Tough on him, but another possibility.
Dear LW2: Now we may be moving towards a post-straight society. Had you not signed your letter as you did, I might never have caught on to this being an opposite-sex couple. Now, the Prudecutor almost makes an interesting suggestion here. But she forgets an important aspect of her own advice. Perhaps conservatives do care very strongly about traditional families. But, in traditional families, the Husband does deliver just as many lectures as he pleases, and the traditionally submissive Wife accepts whatever instruction he deems fit to bestow upon her, with the Children ideally following her lead in this regard.
The real answer is to give H2 what all Republicans want. This, of course, is a Divorce. In fact, his conduct is begging and pleading for it - if he at all has any clue as to the effect of his conduct. He is doing this deliberately in an attempt to induce you to divorce him. And then he gets to run for office, New Trophy Wife by his side, claiming all the while that he was the Victim in your marriage. If you are not so generous, you can refuse to perform such a kind action.
Dear LW1: Now, this is quite serious. You have discovered something you did not know aboutn your daughter, and naturally it has thrown you off a bit. But far more important than whether you warn her off the dangers of sexting (and shame on you for sexist assumptions that only one sex cannot be trusted with pictures of privities) is that you immediately go and enroll in Parents and Friends of Straights, a worthy organization that will see you all the way through your daughter's accidental but now-enforced coming out. That will prevent you from falling into such homosexist traps as calling the genitalia of the opposite sex nasty names. Do remember, however, that PFS is really just a starter organization, and not the be-all and end-all of Straight Acceptance.