"I freezed the frame with the projectile in it. I watched it go back and forth in slow motion, several times. It's too small to be a Boeing 757"

You need to understand how video works. Due to dropouts, I am guessing this is an standard definition analog recording probably made on a VHS or similar product.

Video of this sort is produced by what is known as "interlaced" video. A frame of video consists of two fields - one field being the odd lines and the other the even lines. For NTSC, the standard used in the United States, there are 30 frames per second.

Because of the speed of the object, it appears that the whole image is not available.   

Perhaps the only way to truly tell would be to analyze it from the original tape - not a computer as computer video is progressive scan. It just may be that this video is too short to capture the entire image.