Export Dimensions

I thought I knew this topic well enough but a recent situation has me wanting to double check what I thought and expand a bit.

We're on Avid using DV format (720x480 non-square, right?). I export from Avid all the time for importing into After Effects (into a DV comp) and haven't had problems. I recently exported from Avid for importing into Sorenson and my video looked too wide.

Question 1) Do I need to use different export settings for clips that end up in AE than for clips that end up in Sorenson, r directly to WMV or AVI where it's square pixels only. At first I didn't think so but I'm second guessing myself based on AE using non-square pixels in a DV comp, as opposed to Sorenson which (apparently) doesn't differentiate between non-square and square pixels.

Question 2) You'll notice I didn't even mention what my previous export dimension settings were. Good, we'll forget the past. What should my export dimension settings be in Avid if I'm editing DV format in Avid and I intend to import the exported clip into After Effects for use in a DV comp (which will then be exported from AE back into Avid again). I know the answer should be obvious but I'm just checking.

2b) Depending on the answer to question 1, what would the dimensions be if the end result were going to be imported into Sorenson or directly into some other square pixel only file format?

Question 3) Same situations as question 2... what about the "Display Aspect Ratio" setting? I had mine previously set to Native but now I'd like a more complete description of what this setting actually does. In particular, does it make a difference depending on where you'll be using the exported clips (AE, Sorenson, directly to WMV or AVI)?

Thanks so much in advance for the clarification