FTR,
Here is a reanalysis of the gnd-speed and deceleration of the plane in question using a more advanced method for cases where few data points are available.
The deceleration data point at the 6000 ft runway mark is probably -1.8 m/s/s (the most problematic due to the limited view in the video).
Also included, the average decelerations, to 40 knots, for SWA1248 and 2 prior flights to SWA1248 at Chicago.