Eliminating chemicals from your diet will only help I think, and most junk food is laden with it. After that it's very much an individual thing which you'll have to explore. I find wheat is literally poision for my mind.
I would advise you not to go extreme in any direction with your macros. The relationship between macros and mental health is very much an unknown, and it's better not to be a guinea pig! Personally low carb high fat wasn't good for me and I'm happier eating bits of everything (including starch and dairy).
I also wouldn't restrict things too severely, because the last thing you want is to project your mental health issues onto food and get obsessed with it (easily done!)
Just eat real foods and see what happens, but if you really want a piece of chocolate, don't deprive yourself. Aim for balance.
Welcome to teh forum
"I think the basic anti-aging diet is also the best diet for prevention and treatment of diabetes, scleroderma, and the various "connective tissue diseases." This would emphasize high protein, low unsaturated fats, low iron, and high antioxidant consumption, with a moderate or low starch consumption.
In practice, this means that a major part of the diet should be milk, cheese, eggs, shellfish, fruits and coconut oil, with vitamin E and salt as the safest supplements."
- Ray Peat