It might also help to use good washer fluid. Prestone Deicer has slightly more ice melting power than the blue (-20F) stuff, but it's a slight improvement. If you live in an extremely cold place you might be able to buy even better fluid.
It's looking like a retrofit may be the best option along with adding an HID kit to the fogs. Leaning towards the Morimoto D2S kit from TRS , but still reading around trying to get a good understanding of the process and differences in kits.
I know they are not the fotm LED's but they work great and they dont ice up with the halogen heat.
Either way you want a dedicated "fog" pattern beam, low and wide with a good cut off. Mount them as low as possible. I had 4 of these mounted low on my old Audi 4000k quattro while working ski patrol for a couple of winters, freaking awesome lights.