If we get the 60TH/s online (conservative) in late April, and the hashrate of the full network from that time is 200TH/s which linearly increases to 1,000TH/s in late December. (200+1000)/2 = 600. So we will have 10% in average of the full network from late April to late December. That translates to about 88,000 Bitcoins total mined. That is 0.22BTC/share of gross income in eight months.
Admitting net is 90% gross (which from the looks of various debts, full teams working etc won't be the case) and admitting that Bitfountain itself gets half that, we could reasonably say that ASICMINER shareholders will be earning back via dividends .1 BTC over the course of the next 8 months.
Each share earns 1/400,000 of the profits. If the profits are 88,000 BTC, then each share would earn 0.22BTC.
Net is 90% gross - that sounds ok.
But I don't understand why you assume that Bitfountain gets half of your share profits. Bitfountain owns 200,000 shares which is already accounted for.
Your error in the beginning means you are off by 50% through out all your calculations.