Personally I think it’s okay to have some treats - it's unrealistic to think you can cut them completely. If I were you, I'd focus on having sufficient meals during the day and then allow yourself the option of a small treat in the evening. If you're not actually hungry, the treat will be a genuine choice, and you might find yourself starting to not always want it.
Food is so difficult. I've been addicted to other things and gone cold turkey. But food is always always going to be part of my life, so learning how to stop addictive behaviours, binging and restricting, is really key, I think.
Magnesium helps me with sleeping. I take a combo with l-threonate, taurate, and glycinate. I also add l-theanine. I take l-theanine with my morning coffee, too. Since listening to Stacy Sims, I'm also adding a daily dose of creatine. She says it takes 3 weeks to really feel the effects, but one of the key benefits is better sleep.
I also find eating sugary things in the evening makes my sleep worse and I'm more likely to find it tricky to fall asleep.
But overall, it sounds like you're doing great! I might also ease in to 5mg by doing 3.75 first. I can imagine it could feel like a jump!