Potash is fine to soak in, but like all things unknown to you and your body, start small and build slow. I suggest you to add two tablespoons in 4 cups of warm water and soak your feet. If you have any tingling sensation remove your feet and dry it immediately. If it works, you can increase the amount.
I would not worry too much about sleep. This is one symptom we faster s cannot do much about. I do feel better by rubbing peppermint or lavender oil on my forehead, behind the ears and chest, which made me sleep better.
I also would not worry about day 30, I would only think about today. If you get to day 30 fine, if not, also good because you cleaned your body and mind. Then there is always another time.