Unless my maths is wrong - those points targets are incorrect:
If Huddersfield win two more games than us between now and the end of the season, they will finish above us. That would close the gap by 6 points only You need to remember the games in hand.
If Peterborough win three more games then us between now and the end of the season, they will finish above us. As above but 9 points.Game in hand again.
If Southampton win four more games than us between now and the end of the season, they will finish above us. Is correct
You need to add one more win for us into each of your scenarios.
SO.................