Yes, you got the .wav out correctly.
This wav, is now CBR, not the VBR giving you trouble, so you can use it any way you like.
Womble won't accept .wav, so you need to make it an mp2.
Use tmpgenc to do this, encoding only the .wav audio you extracted, no video.
Womble will then take it.
You could also remux it with your video in tmpgenc.
You can offset the beginning of the audio in virtualdub as well, or in tmpgenc, or Womble, or any other audio editor such as Audacity, Soundforge, or Goldwave.
I would load the avi into virtualdub, click Audio, .wav audio and use your extracted .wav, then sync up in virtualdub (click Audio, Interleaving, and Skew it + for starting audio later, and - for starting audio earlier).
Hit the > button to play, and test sync.
You could then frameserve it to tmpgenc for a proper encode, or not bother, just skew the audio, then save it out again as .wav
Transcode in tmpgenc to mp2, import to Womble for editing (only if needed), or just use the mp2 as the audio track in your DVD Authoring app.