MPEG encoding natively softens video, because of how the encoding matrix operates. Regardless of chipset, encoder hardware/software, etc -- there is always a degree of softening with MPEG.
Looking at the latest post you made, what I see is the JVC black level being a little light, but the Panasonic is also crushing some blacks (coring) the video. Every encoder acts a little different, and this is why many/most TV sets and DVD players come with user-alterable "picture modes" (movie, cinema, games, etc). In some cases, you can actually tweak the gamma and black level without the cutesy "mode" names (as I can do on my Sony HDTV). I'm forever tweaking these settings, depending on the TV channel, camera or DVD (retail or homemade).
On a calibrated monitor, there's little difference in the first and last image. Only the middle image has a definite contrast difference, and for the reasons mentioned above.
This can always be counteracted by over-sharpening the input a little bit, and adjusting the contrast/colors in a proc amp.
Your DVD+R DL issue is --
as long as you're using Verbatim DVD+R DL -- an issue of the layer break. How did you burn the DVD? What programs, what options in the programs? For setting the layer break, my own guide is currently not published. However, this one is similar --
http://www.digital-digest.com/~bluta...pgcedit_v2.htm -- and it might help you.
As you're finding out, video restoration is a game of trade-offs. Some errors can be fixed, but will create new errors. Either find more filters to counter the new error, or look at finding a "good enough" stopping point.