Welcome back! Somehow, I just knew you'd have an exciting story to tell from your time away. Forgive me for laughing.
Time and again, you describe the equivalent of a scrumptious hot fudge sundae, built with the best ice cream and sauces and... then we get to the top and the cherry is ever so slightly askew. And you and Chicken Little run around flapping your wings as if the sky is falling. Get a grip!
I think you have a sense of humor about this, which helps, but geez, you are relentless! I'm afraid that if you don't start eating perspective for breakfast, lunch and dinner you're gonna wear the guy out.
Seriously, what can you do when you get siezed with this insanity so that you can get yourself calmed back down? How about some little mantras like, "Is this REALLY earth shattering?" or "The sky is NOT falling."
Yes, I'm also referring to the recent crisis of S possibly wanting to spend a night at home after being away for a week and going out last night. Yeah, you could try to work out a compromise, or you could just give it a rest. (It sounds like he was trying to be accommodating to your desires, but it's not clear to me that he received genuine reciprocity.) Can you deal with some of your feelings about it without discussing it with S? How much of this is really about your R? How much is about your own issues? Does he really need the play by play of your internal rollercoaster?
Knowing things is a lot easier than DOING them. Find yourself some tools to get you through these things. How about a big old rubber band to wear on your head? You can snap it when your brain starts trying to kill you.
