Hi,
when looking at the VP77 datasheet I think you need to setup the internal registers of this Video Decoder. Otherwise I do not think, that your system will work. Do you have a uC in your system, which does this job? Or do you plan to do it with the I2C interface from an external controller?
The VP77 would be able to support the s-video (means the separate Y and C channel), but from your pinning list I think you can only use CVBS (for the modulated C on the Y channel).
you mentioned Vss runs on 9V. That looks strange for me. What are the levels of the other supplies
regards