Hi Suda - thanks for the update. Although I'm sorry that nothing seems to be resolved. I just want to know that I understand your frustration, and think you're quite entitled to start on the Baileys.
Regarding bathrooms, my SS has some unsavoury habits. Thankfully, my husband and I have a bathroom each, and on access weekends, SS shares with DH, as there's NO WAY I'd allow him to use mine.
I also wish we had separate remote controls, as he literally hugs it, rubbing his unwashed face with it, and hanging onto it with hands that never get washed after toilet visits. It really makes me cringe. When he puts it down, it's still warm and moist (yuk!!!!!) and I dread to think what bodily horrors are sticking to it.
If your husband still insists on offering his son Hotel Facilities for the next 8 years, then I think you're quite entitled to want private bathroom facilities, particularly as he has his own en-suite wet room. It wouldn't be so bad if he had decent habits, but given he sounds completely manky, he should stay out of your bathroom. I mean, if you go to a health club, men and women aren't expected to share the same shower facilities (god forbid), so you shouldn't have to share your home facilities with a member of the opposite sex, that you're not related to. It's not appropriate. As you say, your DH won't budge on his stance, so I think you should stick to your guns on the bathroom issue.
I know precisely what you mean, about DH not mentioning things in front of SS, that SS isn't included in. So I understand your concern that your DH's views on bathrooms may be slipping. But again, as he won't compromise on SS's residency, you shouldn't compromise on bathrooms.
My DH doesn't like talk about non-SS activities in front of SS, however I often do it for devilment. I'll mention a holiday, or day out etc etc, that I know SS won't be going on ...... how petty am I ??!?
As regards your husband not having a problem with his son's presence in the house, I think your hotel room analagy is a good one. My husband is completely relaxed when his son is with us. However for me, having an apathetic, lethargic, unwashed adolescent male festering on the premises, is deeply intrusive and makes me quite uncomfortable. DH often claims "but he isn't doing any harm" to which i reply "my mother could lay on the settee for days on end, she wouldn't do any harm either, but you wouldn't like that, would you" and he just doesn't get it. I've often asked him how he'd feel if some random bloke from down the road plonked himself in our house on alternate weekends. How would DH feel then? But again, he just doesn't get it. However he's quick to complain if my mother overstays her welcome, so I think he understands the "two's company, three's a crowd" situation more than he lets on.
I dind't mean this to turn into war and peace, but wanted you to know that I understand your frustrations, and think its totally reasonable for you to insist on a bathroom that SS can't use.