The point regarding the star comments is not that there are X many chances for something to happen, so it's not a surprise that it happened. The point is that there are likely Y many situations very similar to this once that are likely to occur in the universe, and Y is a number too big to put into any meaningful context for almost anyone of us. We should therefore not be surprised to find life in many, many other places. The odds of Earth the only place where life exists in the face of these odds would be rediculous. That would be, to me, like throwing a puzzle in the air and having it fall into place perfectly.
I am also not sure how we can, with certainty, place arbitrary boundaries on what conditions are needed to create life. We just know what parameters are already in place to create life on this planet compared to apparent lack of life on our neighboring planets (and with sparse information of even these planets). I would not assume that this is the only way life can come to exist in the universe. I'll go out on a limb and that that our collective knolwedge of how the universe works is much closer to 0.1% complete than 100%.