Something new on the IVTC-issue:

Get the DeComb-package, and then you can just use the Telecide(1) command in AviSynth. So you no longer need to separate and weave the fields manually. In the script this would be enough:

I don't know if the AssumeFPS command is really necessary, but without it the resulting clip only has a framerate of 23.970 ... which, I think, wouldn't work when creating a DVD out of it. But you should try it, and check, if the audio is in sync.