Hi, welcome to JustAnswer. My name is***** am a ticketed HVAC and refrigeration technician with over 13 years in the trade, and I will be helping you today.
Thank you for your question. The factory setting for refrigerators is 37F (or 3C), so I would recommend changing your cooler set point to 3C.
Regarding your vegetable tray that is freezing the lettuce, could you send me a picture of it? Thank you.