How should I insulate a poured concrete exterior wall?
I would glue durafoam to the concrete first like you said.Then like you said put up a wall using 2x4s for the 3 1/2" insulation. Then use unfaced insulation,then a vapor barrier then the sheetrock. If you want to use paperbacked insulation then do not use a vapor barrier afterwards before putting up the sheetrock. If you put up two vapor barriers there will be a strong possability of trapping moisture between the vapor barriers. And moisture means mold.