All that we really know, based on the evidence that has been made public, is that Vincent Foster did not commit suicide in Fort Marcy Park. Suspecting the Clintons of murder is a reasonable conjecture, but without any proof. The real mystery to me is why two Republican special prosecutors lent their name to the cover-up.
Mrs. Clinton and those silly F.B.I. files?
And maybe a threat of the same happening to them?
I don't think you have reviewed all the evidence that has been made public (granted, more should have been, and more should have been developed by law enforcement). But there is more than enough out there to conclude that it was indeed a murder. And furthermore, since suicide is not a crime, there would not be the massive, multifaceted cover-up if (hypothetically) it were a suicide. Recall that many individuals have been convicted of murder without a living eyewitness to the event and without a confession.