Export end up blurry

Here are some good settings for high-quality export. Then if you want an Mp4 to take it into Media Encoder. 

Swf keeps the vector data so quality is not affected by resolution.

Mp4s work with pixels, it rasterizes your animation based on the stage resolution.

640x480 is a pretty low res by today's standards. To get a sharper image all you need to do is increase your stage size (ex. if you want a full 1080p video your stage size should be 1920x1080). Export it, and you'll instantly get a higher quality video.