You ask why I claim you use current market cap as the basis for future valuation? Uh, because your entire post is based on it.
Your future share price valuation numbers/calculations are based on current market cap - which of course is complete gibberish. There's absolutely no relation between current market cap and future share price in the open market.
Future share price will be based on earnings per share times a multiplier. Current market cap is completely irrelevant. If you want legitimate future share price estimates - use EPS. Run those calculations.