I don´t know exactly where is your problem, for my dvds I also use dvdlab, my tv captures are edited in virtualdub and then encoded exactly as you´ve done with tmpegenc but in the settings for encoding I use "ntsc dvd" with pcm audio and for the output file separate streams, some time ago used to encode with mpg audio with a 128kb bitrate this works well in dvdlab but then I found out with a friend´s standalone dvd player that not all models are capable to play mpg compressed audio so now I only use pcm.
Hope this can help you.