No, Leafs are 4 points back with no games in hand after tonight.
Actually, if the Leafs were to win tonight, which is a fairly large if at this point, they would be 2 points back with no games in hand. Montreal and Toronto play in the last game of the season, so if Toronto wins out, then yes, they would have the fourth seed by virtue of ROW, or if it goes to the second tiebreaker, H2H record vs the Habs. Hence, they control their own destiny.
I've never seen a game where the Sens weren't involved talk so much about Karlsson. You know he's one of the best in the game when the announcers keep talking about his return when it's a rival team playing.