So if it went down exactly as you said, you can relax, you don't have to worry about any extra bills to pay.
Two things that are important here are that the "official" valuation of the stock is what company counsel said it was, and if they had changed the valuation of the stock, unless there is only 'preferred' stock (unlikely) your common (likely) stock hasn't changed value at all.
When you did the last stock exercise if the CEO mislead you on the price it is their problem not yours.
Finally, and this is really really important, when you are not publicly traded the stock can be worth anything you say it is worth. The 409a process is one which allows the company to have a way of valuing the common stock but it doesn't come into play, generally until you have enough investors to make the calculation significant.
Two things that are important here are that the "official" valuation of the stock is what company counsel said it was, and if they had changed the valuation of the stock, unless there is only 'preferred' stock (unlikely) your common (likely) stock hasn't changed value at all.
When you did the last stock exercise if the CEO mislead you on the price it is their problem not yours.
Finally, and this is really really important, when you are not publicly traded the stock can be worth anything you say it is worth. The 409a process is one which allows the company to have a way of valuing the common stock but it doesn't come into play, generally until you have enough investors to make the calculation significant.