Greg,
Reading your post, it appears to me you are simply importing mov/avi files into premiere pro, effecting them, then exporting from PP.
Question: Look closely at source movie that you are creating with Camtasia, etc, and see what it is? I'll bet it's a 15fps movie already. So Ideally you'd be best to create a 15fps project in PP and in the same dimensions, etc.
Exporting directly from PP to flash isn't ideal for High Quality, see adobe's article:
http://www.adobe.com/designcenter/dialogbox/encode_video.html
As far as interlacing, if the source isn't interlaced, (from Camtasia, etc) then you won't ever have to de-interlace, unless you are exporting NTSC video/footage. Also,if you are intermixing source material, interlaced and non, you can right click the clip in CS3-CS4 (not sure about CS2) and treat the fields differently for that clip (so that all clips in your timeline are the same!)
Richard
