Are you certain that Genesis was written as a chronology? There are other genealogies written by the same author (God via Moses) of parallel lineages that are not equal in generations or years - i.e. same starting generation ; same ending generation but one line has more generations or more years. Did Moses forget how to add or siimply make a mistake? Or could it be that the geneologies were never intended to define the age of the earth but rather a hereditary line of decent; that Jesus decended from Adam through Abraham, through Judah, through David as prophesy predicted.
Are you certain there was no physical death before the fall? Or was that about spiritual death? Which is more significant?