When No-eul enters the hospital room, there's the steady beep of a heart monitor but Na-yeon isn't hooked up to any such device.
The Mardi Gras festival takes place on the lead up to Lent, which is in late March to mid April. The date of the festival in Squid Game occurs right before October 31, Halloween.
Storing firearms around any water or faucet is a terrible idea, leading quickly to rust and corrosion and risking misfires when needed most. Only under water would be a worse place than a bathtub, even one in an abandoned motel. Better that he would have stored his arsenal on the bed and the cash in the bathtub.