Uhm, I think that I know what the problem is...most likely, your DVD is PAL, so fps is 25. You can't IVTC it, you should just deinterlace it. Also, using assumefps to change the framerate will speed up/slow down the frames. In order to change the fps and keep the audio sync you should use changefps or convertfps (the first one will add/drop frames, the second one will blend frames... if your dvd is actually PAL and not NTSC, I highly discourage the second one, since your dvd most likely already has a lot of blending).
Also, I found that besweet doesn't convert ac3 to wav really well at times. I personally use besweet just for mp3 compression. If you need to convert an ac3 stream to wav, my personal suggestion would be getting
dBpoweramp and then follow
this to let it read ac3 files. After that, follow
this guide to convert it to wav.
For audio files that winamp is able to open, though, I use that (winamp can't open ac3 files properly, though).