Ryan,
You’ve probably confused us (including David) with your title “exporting SD video
to DVD” and then later in your post you are asking 2 different things;
SD to DVD and HDV 1080i to DVD (standard DVD).
There is an article/tutorial just released on Ken Stone’s website,
if you want to go from HDV to standard def. DVD,
basically, the way to go is to export your HDV from timeline to ProRes 422,
then that file to compressor and finally to DVD SP.
The link is here:
https://www.kenstone.net/fcp_homepage/hdv_timeline_to_sd_dvd.html
If you were only asking about SD DVD then the only route to go is as David told you;
SD from timeline to QuickTime movie (not with conversion).
Mio