Look, if the problem is overcoming some communication hump and there's only one player trying to articulate here (however struggling) you and your group of people aren't going to get over the hump.
Not on your own -- because if you could, why would you be posting in the first place?
Not with you posting on here -- because basically you have to pick from this:
You have to decide if you
A) value strict monogamy more
B) value being with John more.
Because without more information from other parties we can't go "Well, you are putting her in a place of having to pick A or B. Have you noticed you are willing to ____? That would give her the option of C. Have you guys considered that?"
You are sounding like you are still flip flopping between the two and not ready to pick. Largely because you know you cannot have strict monogamy without leaving John. He won't give it or at least doesn't sound like he's willing to give it right now.
And largely because you don't know what KIND of open relationship model parameters he IS willing to give because he's not articulating that.
You are having a hard time articulating an open model you could live with because
a) Your trust has been broken, and John and Sarah are not yet articulating how this will be considered and repaired. So why would you want to sign up for something at this point where your return on your investment is not clear? Of course you do not. Not even if you design it! It requires their buy in and their promise to stick to agreements.
b) Your few attempts at designing some offers yourself are still in the "rough draft" place. Because you feel like you are stabbing in the dark trying to take them and their wants/needs into consideration (and you get no feedback) and you are not sounding comfortable asserting yourself and just stating "Well, how about THIS then? For the next 3 mos and then we adjust it at the checkpoint if it doesn't feel right. Because you fear resentment/accusation of micromanaging ang you are tired of being the referee.
You are very stuck on the kissing hello/goodbye. I see that you value that. I also see you fear being outed.
But John is bugging you on it without offering anything. Have YOU offered anything -- "Can't I have this mouth kissing greeting just for ME? Why can't Sarah have a hug and cheek kiss?"
Because I sense you have a need to be primary, recognized as primary with something saved only for you, and in public displays of affection, you need their expressions if accidentally seen to still be able to "pass" as close friends.
Is THAT the reason you struggle to articulate for the kissing greeting?
I don't view ANY of you as bad guys. Right now I view you as a bunch of people in a big mess.
You write this:
I want to be in a relationship with my husband, not chaperoning him.
Ok. Stop. Let him own his part in this. Just report your own internal emotional weather. State what you are and are not willing to do right now. Perhaps things change later. Perhaps they don't.
Take a time out and just be "The Weather Channel" when asked. It's too hard for you to see or do anything in the middle of the storm. So... wait. Give it a week and see if things look different or you feel different or variables have changed.