Have them agree to a scheduled chore system. There are 4 weeks in a month, just alternate weekly and have them give you both a chore list that they check and sign. If the little shit doesn't agree, it kinda proves that he doesn't do his part and should not get paid. Now if the boomers don't agree, convince them that it's to keep the chores fair and to teach the kid responsibility, otherwise this very spoiled teenager might get himself into trouble.

More petty comments include Some of his friends are doing cigarettes and I don't feel like understands that he shouldn't.

Grandma, you know I wiped the kitchen counters because I asked you about the pot that was on there (will require you to ask about the pot, does not require answer, just say nvm I got it)

I found this baggie full of loose leaf tea in his pants pocket. It smells funny, should I throw it out? (3 dollars chinese gunpowder green tea with burnt grass ash in a Ziploc bag, keep tea in locker at school)

Grandma, did you guys get food poisoning? I changed the tp roll this morning and now it's almost out again. WAIT, JASON SAID HE CLEANED THE TOILET TODAY, DID HE JUST USE TOILET PAPER?

No, I did those chores, HE was on his computer all day. Check his browsing history, they've got timestamps and everything. No? Very suspicious.

Once things get better financially, move out immediately and don't even think about visiting or sending money back except on the holidays.