Do de do....
By now you're discovering that unless you're in HiDef, you can't get a still any better than about 5x7 inches without the image falling apart.
You're also discovering that standard television is interlaced with a slow effective shutter speed which means it doesn't stop motion any too good. Most if not all of your captures are going to have smearing or dual pictures with comb artifacts.
You can suppress that, but not get rid of it totally with the deinterlacing tools inside Final Cut.
Standard television, when stopped in its tracks, has about the same image quality as a one-third megapixel camera. Not Three; One Third. The only reason it works at all is Lucile Ball and Milton Berle, the pretty colors, and the fact that it's all in motion.
Koz