The AC3 filter will do nothing to help playback on your stand alone dvd player. It might help you play back the finished video on the computer so you can see if DVDFab is encoding stuff correctly.
Another way of testing the output is to use VLC media player since it does not rely on outside codecs. www.videolan.org
If it doesn't work in VLC there is no point in burning to a disk. See what I'm getting at? When working with encoding/transcoding, always test before burning.
You may very well have to start over. But I can't tell from long distance what went wrong.