If AMBS was trading at 0.20 and there is a 1:1 spinoff giving shareholders and equal number of shares in the spinoff, the AMBS price should drop to around 0.10, not 0.01.

It would be similar to how a mutual fund share price drops by the same amount of their regular dividend distribution. Your investment value would remain relatively the same before and after the spinoff, and market demand would drive share price of each company independently at that point.