How much video & audio bitrate do I need for dvd videos?
More than 'what do I need', you should ask yourself 'how much am I allowed'.

This page mentions an average bitrate of 4-5 Mbits/s, this is audio + video + subtitles. It also depends on the length of your content (as you also have a maximum capacity of about 4.7 Gb for a single layer DVD-Video).

FLAC is not supported on DVD-Video, common audio codecs are MPEG1-L2 and ac3.