Your belt is correct. Your setup also looks like mine. I don't think adjusting the chain will make a difference.
I'm pretty sure your hub TC needs to be disassembled and cleaned. Videos like this will guide you:
https://www.youtube.com/watch?v=C9yPHtfJO9w
Here is a manual for the comet:
http://www.*************/PDF/Comet_TA..._Converter.pdf