Personally, I use the decomb plugin with AVISynth for IVTC - Telecide() and Decimate() - never gone wrong for me yet.
Does DGNVIndex not tell you whether the fields are repeated or not?
In terms of encoding to BD spec, using x264 I either go with the pulldown option, or if your content is high enough quality, upscale to 720p using nnedi3.