compression and aspect ratio

Hi ...some after effects questions.... How can I make widescreen 16:9 footage which is intended for final output to DVD in after effects?.The source material is all standard definition not HD .I have been using NTSC DV widescreen 720x480 with a pixel aspect ratio of D1/DV NTSC widescreen frame aspect ratio 9:5...
any footage I have used and created has not been widescreen 16:9 its 4:3 and I stretch the layers to the safe zones in the comp...it definatley plays widescreen but I dont know if thats true widescreen that will be played back properly on a 16:9 tv or widescreen computer monitor. And should I be setting pixel aspect ratio to square pixels?? when I have changed to square pixels it either stretches the image or makes it smaller...
and if this is correct should I set the render output settings for quick time to lock or preserve aspect ratio or use the stretch option to achieve the 16:9 aspect...only because its not hd which is natively 16:9 I think. I want to use final cut express, sorenson squeeze and DVD studio Pro to author the DVD...any help would be great
thanks