Assuming your yield and property values assumptions are correct, you actually need to divide the total fiat returned to investors by the total number of coins (keep in mind that 10M totally are issued, including the 1M for founders' compensation and 0.5M for contingencies).
So you get a total return of USD 99.176 over 30 years per coin for an investment (at USD4000 assumed BTC value) of 10 USD.
Of course this number is an average and only applies to people eligible to half of the capital gains, meaning people selling before 30 years will get less, people not eligible to the capital gains will get only USD 44.43 per coin.
Chris, can you confirm this calculation?