Not using drugs is easy. He has something better than drugs.
Not doing sex work is harder. He doesn't have another way to earn money, except for shoplifting, and he's pretty sure shoplifting would also be on the 'no' list. But he can sleep in Asher's bed and eat Asher's food, and Ron pays for his phone, and most things he can made a sad face around Lev and Lev will buy it for him, and Rachel shares the money she earns with him just like he shares his food and bed with her.
Not fucking guys older than him is almost impossible. He doesn't, of course. He jerks off a lot, he fucks Rachel, he gets punched out by a guy with super-strength. He does not seduce Z no matter how hot it would be to fuck someone else who can heal. He does not open Grindr or sneak down to the pier or smile back when a guy cruises him at a bar, even though he knows how easy it would be to find a guy twice his age with a big dick and blonde hair and blue eyes and a smile that makes you feel loved.
Chris already gets tested regularly; it makes Ron happy and Ron buys him ice cream afterwards. But he gets tested before Ron would start nagging him about it, discovers he has chlamydia, and takes his meds as scheduled. He stops trying to get testosterone. His period comes back and it's. Okay. It's fine.
Rachel is confused. Rachel is really, really confused. He tries to explain it to her and it doesn't work at all. She misses him a lot and it makes him sad, especially since she doesn't understand at all why what he's doing is more important than her. He talks to her every day, sleeps cuddled up with her in a real bed every night, convinces Lev to buy earrings that match her eyes, punches out a guy who thought he could get away without paying, and none of it helps.
Ron is also confused but not going to object to any plan that sounds like it means Chris will still be alive when he's 21.
He avoids Asher. Lev and Sasha say Asher is fine with it but Chris is suspicious that he just forgot that there are an additional two teenagers in his apartment eating his food. It seems like the sort of thing you don't want to draw to a billionaire's attention.
He avoids Laser. He's pretty sure he's not the sort of person who's allowed to interact with five-year-olds.
Chris Parker stopped paying attention in school in seventh grade, so Lev has to go back to basics, and then to even more basic basics, and then to things Chris really should have gotten in elementary school. Chris would feel bad about it, if he didn't know that he was smart; it's just that he had always had better things to do than school, and now he doesn't. He studies for ten hours a day, curled up on a couch with a pen in his mouth and science textbooks scattered across the floor. It starts out as something he's doing for Marlo, to make Marlo say he is sweet again.
To his surprise, he discovers he likes it. He likes the austere beauty of mathematics, the feeling of solving a puzzle. He likes learning about what people were like in other times and places. He likes the way that science all makes sense-- it's a system, it's not a collection of random facts that have to be memorized, it all fits together. He writes essays and Ron reads them and ruffles his hair and says that he understands. He cries reading the Well of Loneliness, dislikes Maurice, complains that the Picture of Dorian Grey doesn't have enough fucking in it, says that the Story of O would be way hotter if it were gay but it's pretty good as it is, and objects to the Marquis de Sade on the grounds that there's better porn on Literotica.
When Rachel is off with a client and it would be so easy to download Grindr, he cuddles a pillow to his chest and says to himself: sweet sweet sweet.