here are the answer How much quantity of the mixture should be applied on the scalp? it will vary on each person. You just apply the amount needed to cover your thinning scalp area. Try 1/4 tsp at first.
How many hours can I leave it on my hair? Can I apply overnite and wash in the morning when I wake up? The article said scalp massage for 2 minutes then use warm towel to wrap your head. I don't think you should do it overnight.
is there any side effect, if the mixture that you have mentioned is not accurately mixed? I don't think so, just make sure that buy is essential oils not fragrance oil. :)