Schottenheimer never played against #7 seeds in the playoffs. If you look at McDermott’s record against non-#7 seeds, it's 3-7; a .300 winning percentage.
Yes, Josh would have kept Bowles or Jackson employed, especially if they were competing in this division.
If you put McDermott on this year's Saints, they wouldn't make the playoffs. If Josh were their quarterback, they would at least clinch a wild card.