BS options val, page-3

With respect, technically, the interest rate used should be a relevant 'risk free' rate. In a low interest rate environment, the chosen rate will have minimal effect on the ultimate pricing in any event.

Voltaility - again, strictly, it is the future implied volatility of the underlying security. Whether one uses 80% or 100% is largely moot in any event as this whole exercise is theoretical. Noting, the BS model has flaws galore!