Hey Huckleberry,
Sorry that I have not gotten back to you, but I just don't have time to delve into every debate that has been going on.
In regards to your question though, I think my last post about the difference between the general Protestant view of salvation as extrinsic imputed justification verses the Catholic view of salvation as beginning with justification but being complete only in sanctification is relavent here.
If I were to answer your question directly I would say, I don't think the Bible necessaarily promises us absolute assurance. It is true for instance that passages such as 1 John 5:13 speak of "knowing" that we have eternal life, but I don't know that we should take that to mean we have a guarantee beyond all doubt. I think it has to be interpreted alongside other passages such as "Not everyone who says to me, 'Lord, Lord' shall enter the kingdom of heaven, but He that does the will of my Father" (Matt. 7:21), or the last judgment scene in Matt. 25:31-45 when both the saved and the condemned are surprised by the judgment they receive.
I think taking a position like St. Paul seems most reasonable and saying that "in hope we are saved" (Rom 8:24). Meaning, yes we trust greatly in God's love for us and His abundant mercy. But we also continue to "work out our salvation with fear and trembling" (Phil 2:12).
The dividing line comes down to a fundamental difference in our understanding of salvation. I think you worry that if I say I don't have absolute assurance it means I am somehow doubting Christ's work as my savior. But I think the reason Paul could say something like, "I control my body, and bring it into subjection, least that by any means, when I have preached to others, I myself should be a castaway" (1 Cor 9:27), because He realizes that although Christ is perfect in His mercy and redemption, I still have a role in accepting it and conforming my life to the cross and resurrection of Christ. Hence my above quote, it is not just saying "Lord Lord", but also, with His grace, doing "the will of the Father".
So my unwillingness to say that I have absolute certainty is because I know that it is possible that in my weakness I could deny the Lord's mercy or fail to do His will. Again, that doesn't mean I don't live with confidence, but it is a confidence of Hope that God's goodness will sustain me beyond my own weaknesses, but not the assurance that says I might never turn away from Him.
I hope that answers your questions somewhat