I don't see anything to worry about in this case. Child support cannot be ordered retroactive to before the date of filing. For example, if she files for support on April 1, 2011, support could later be ordered retroactive to April 1, 2011, but no sooner. As long as he resides in the Philippines, the U.S. courts do not have jurisdiction to enter a support order
Secondly, a court would not order support for him at 18. He would be an adult; the window is closed.
The bigger problem for him, though, is that it is basically too late to establish paternity. In California, after the child reaches the age of two, the court looks to who the acting father is of the child, not who is the biological father. The kid is 14 years old and you have no relationship with him; you may have been the kids "sperm donor", but that doesn't make you his father under the laws of the state of California.
She would basically fail on all levels of this endeavor. I do understand why this has caused you anxiety, but I see no reason for concern from a professional perspective. I hope that this helps.