No problem Jedeitor
Well, for lossy DTS the "cap" is 1536kbps and this DVD had half of that, hence "half-bitrate" of 768kbps. You are correct that anything above that bitrate of 1536kbps for the core, is used for lossless DTS-HDMA tracks.
I have already sent the converted audio to Andrea.
I think that it could be replicated from the 5.1 mix, as this is a 6.1 Matrix and, really, the center surround is "uniquely" created from the left and right surround channels. This would be different if this was a 6.1 Discrete mix, as at that point (most likely) it would be a more "unique" channel. There's a lot more "tech-babble" involved here but I just don't want to get into that right now, LOL
HOWEVER, I did do some tests and tried to "re-create" this "extra" channel from the 5.1 mix that was sent to me as "sync-reference," and I noticed that I couldn't completely replicate the extra channel that is present in the 6.1 DTS mix. It was close, but always seemed like it was lacking some fidelity. Speaking of fidelity and, of course, dynamic range, clarity, the DTS-ES track blows the the AC3 track out of the park. When listening to certain parts of both sources on my surround sound system, I noticed a lot more action in the LFE, slightly cleaner dialog, and very nice use of panning for sfx with some very nice use of the surrounds on the DTS track, whereas the AC3 track (although not bad) lacked a little bit there but, at times, the front left and right speakers were a little cleaner in the AC3 track VS the DTS track where I noticed a little bit of distortion but very briefly.
As far as "isolated score track" is concerned, honestly in case of isolated scores tracks in general, there are usually sfx present with the music. this is not always the case and at times can be done by replacing parts of music using actual CD material, but it's a pain in the ass. I have been working on a LOSSLESS "isolated score track" for "the matrix" for about a year and had 90% of it done months ago, but that last 10% is a nightmare because the music was uniquely mixed for "that" part of the audio track. In cases like this, where no other source is available, some major "tricks" have to be played and they have such mixed, inconsistent results that it's a nightmare to work on. Eventually, I'll complete it, but I don't know if I see myself working on another one after an experience like that. There are better uses of my life