Put Merrill or Severson out there and they're bound to make mistakes. Difference is that their rookies. Not only is Sal slow but his decision making during PKs is very rookie-like.
If I'm Lou I start shopping either Larsson or Gelinas to see if I can bring back a solid stay at home D. We don't have that.
Any player playing those minutes will make poor decisions. It's guess work and positioning. Only one other player in the league had more PK time last season than Sal's 3:58 per game, and that was Coburn's 3:59. If he was as bad as you say, the Devils PK would have been a lot worse with him out there so much.
You can't just toss a rookie into these situations and hope for the best.