I began reading your letter and at least through p. 11, you are simply rehashing the typical attacks of Calvinsim/Reformed theology towards what you feel is Arminianism/Semi-Pelagianism. While I absolutely acknowledge that we are dead in trespasses and sins, the NT is full of appeals to "repent and believe" and, amazingly, Jesus Himself was recorded in the Gospels as saying at different times that "your faith has made you whole/saved you."
While you do not provide quotes concering Buchan's lack of defining "born again" which may indeed be true, it is quite possible that you are really more offended that he is not "Reformed" enough in your estimation. It amazes me that so many professing Calvinists/Reformed theology proponents easily dismiss calls to faith and belief in Jesus Christ as being anti-Biblical. The Bible is full of imperatives (i.e. commands) to do this/not do that. This is part of being created in God's image. Why should not a call to repent and believe in Jesus Christ be the means by which the Holy Spirit enlightens someone? Be careful that in your desire to correct what you feel excessive that you yourself are not upholding an excess of a different kind.