The only suggestion I would make is the use of a better LD player. Lesser models like the 91 can cause a lot of the video noise that you're seeing.
Consider using something like the CLD-97, which has excellent composite output. You could send that to a capture card with a top-of-the-line comb filter. I think that would provide the best results.
The component mod you've made to the 91 is intriguing though. What kind of comb filter/transcoding solution does that employ?