The f.lux interface is customizable for almost every schedule. In every version of f.lux available now, you can control your sunset light levels and color temperature. That doesn't mean it's immediately obvious, but it is possible. The criticism of not enough documentation is absolutely fair, and it's on the to-do list. Until it's available, post the timing you want and are having trouble with, someone will try to help you.
Unfortunately, it goes beyond the scope of an internet forum to provide advice about treating medical conditions, and we've crossed into that territory in this thread. f.lux does not give medical advice.
Before I close this thread, I want to direct you to CET, the Center for Environmental Therapeutics, which specializes in this area. They offer excellent research-based information for both clinicians and patients: https://www.cet.org/
