The amount (and degree) of variables is so large that the exercise is essentially worthless. How can you estimate the share price or probability of exit?
You can't really but if you were to think about it that's how I would go about it. You can test different values and probabilities that you think are (likely|conservative|optimistic) and go from there. That gives you a range and a ballpark for different scenarios.
Personally though, if I can't predict something with > 90% accuracy/reliability then I'm not interested in investing in it.
Personally though, if I can't predict something with > 90% accuracy/reliability then I'm not interested in investing in it.