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'm glad mushrooms are against the law, because I took them one time, and you know what happened to me? I laid in a field of green grass for four hours going, "My God! I love everything." Yeah, now if that isn't a hazard to our country..."
― Bill Hicks
"Sometimes eating the wrong food with the right attitude is a better choice than eating the right food with the wrong attitude... That’s how powerful the mind and the heart can be in the healing process."
- Chris Kresser