I think the basic problem is that Luther (and Lutheran theology) does not put a premium on being systematic. Instead, it it exegetical. Thus, the categories you employ are largely foreign to Lutheran expression. Second, Luther's opinions, and the writings reflecting them, changed to some extent over time.
My understanding, to try to put it in your terms, is that Lutherans do in fact believe in "total depravity," if you mean that humans, unaided by God, are incapable of embracing the Gospel (coming to faith). That is, we are monergists. That said, we affirm that grace is "resistable," if by that you mean that if the Gospel is preached and an unbeliever does not turn from his unbelief, the fault lies entirely with the unbeliever and his wickedness, not with God. To the extent there is a logical contradiction there, we accept it as a mystery, because Scripture reveals both truths.
Lutherans believe that God wills that all humans be saved and that Jesus' sacrifice is sufficient to save all, which makes Him the Savior of all ("objective justification"). However, not all come to faith in Him (the "saints"), and fewer still preservere in the faith till the end. This last group, who preservere in the faith till the end of their lives (or until Jesus returns) we believe God elected from eternity (the "elect"). Thus, we do not believe in the necessary "preserverance of the saints" (one can lose one's faith), but in the what might be called the "preserverance of the elect."
Here's a link that gives a brief summary of LCMS teaching on the election of grace.
http://www.lcms.org/pages/internal.asp?NavID=576