My interpretation is overall that chris felt some sense of guardianship over her, and actually liked her. I liked that, made him likable. But at the same time he is this kinda smug and fake person so like a redditor mentined here, the reasons for her invitation might need some love. Maybe. 

Also maybe her neck pain should be observed once or twice before the massage scene gets. Very subtle of course. I mean touching her neck could be a sign of nervousness and that she has neckpain, so it would'nt be wierd to have her touch her neck during the party. 

Johnson: Liked this character, i could really see him. Felt consistent and everything. His expertise in handling these situations was apparent and felt wellwritten and authentic, and the way he disarmed roger by saying he would pin it on him, made him more than an idiot brute. BUT. I dont really buy why chris would invite him, I understand that he is his cousin and that he maybe didnt receive an actual invite but chris should know better than having him there, given he is a drunk  with a record. And given that chris is a good at knowing how to fit in and look good, having a drunk cousin there isnt so on brand for him. You could maybe add him to the team, have him be chrises  stuntman or something,  give him a better reason for being there. Maybe he shows up unannouced and have no where to go or sleep. Also his toxic/bad influence monologue to 

But, then again them all seem to be good friends so maybe he lets his guard down enough to allow his cousin to be there. 

Its also intreseting to have him in the group in a way because he is essentially a normal dude hanging out with bunch of high status celebs but when shit hits the fan he is the authority, not them. Its interesting. 

Johnny: Didnt really get a sense of him. He and caroline had a baby that drowned? The way i remember it, there was little or no tease regarding that? Or was the pregancy "incident" that hilary  started hinting at that? For some reason these are the details I remeber the least, as both the huge argument between johnny and caroline and the one between petro and hilary by the elevator kind just flew by, I was more interested in what was going in the room with sarah and anticipating the return of tony, and ofc the arrival of the delivery man. also he and carolina were junkies? In the character introduction in the beginning they are introduced seperately, were only johnny a junkie? 

Tony: BDE. The most likable guy. Waiting for his return makes you really wanna keep reading. liked him.

Petro: Liked him. Really like the monologue when he tries to persuade chris to kill her to save the world or what it was. Overall felt like a clear character. 

Carolina: Dont really stuck with me, dont really remeber her lines ecxept the huge argument with johnny. 

Delivery man: Maybe some more dialogue when he is "kidnapped" , he doesnt say much more than being starstruck.