Spongy brake pedal is probably due to old fluid and/or air in the lines get a full brake line bleed.
The new shaft will take care of the ABS issues.
Think about it, how can a driveshaft in an independent front axle affect brake feel? It can't. Then again if your wheel bearings are so bad that you are getting knock back then that may be the cause.
Does the pedal firm up after a couple of successive pushes?
