An impulse, by definition, has a length of 0 (it's instantaneous). This is impossible in a bandwidth limited system, so one would expect to see something a little bit longer...but it shouldn't be longer than say 1ms - certainly not 100ms.Isn't the 100ms that you refer to a function of the duration of the impulse response analyzed?
Are you saying that you only did the sweep up to 200Hz? If so, that might explain it. Why aren't you sweeping to the top limit of your soundcard?
Regardless, simply increasing the volume on the BFD is going to make it seem like it takes longer to decay. The fact that your EQ shows the same thing simply verifies that it is achieving an amplitude change...not so much changing the ringing at that frequency.