Have you tried high doses of valerian root, its a herb but it helps people coming off other stuff, I've used it to come off loads of different meds, benzos tramadol, zopiclone, mirtazapine etc
Also try essential oils for sleep like lavender and geranium oil, there's loads for sleep and low moods, sounds funny and hippy dippy but don't knock it till you try it, and horlicks and bedtime tea, like pukka night time tea, worth a try
Failing that have you tried low dose 7.5mg mirtazapine, it's a sedating antidepressant, helps with PAWS as it has studies showing it can even help with cravings for other drugs, it's used in addiction therapy and it's one of the best sleeping pills I've tried lol