Yes, the ZipSeam is washer and dryer safe, in fact the fit you created using the ZipSeam should stay in place unless it's on the rigorous cycle (which you should avoid on dress shirts to prevent excessive wear)
Since you don't need a needle or thread to sew the new seam, you can reuse the same set of ZipSeams on all of your shirts or just use one set for each shirt. You can also adjust the fit as you gain or lose weight, whereas traditional tailoring methods would take forever because you would need to unstitch the previous seam.
Unfortunately in most cases the answer is no. Most jackets have multiple layers which makes the material too thick for the ZipSeam