The results explain the envelope/volume bug and the combined waveforms.
Yes, very nice job!
This gives accurate information about what should be avoided when using the DTV SID. I wonder if it will be possible to actually use this when patching games, to work around DTV SID bugs. I remeber trying "Jammin' II (Beat It!)"  on the DTV, and the sound was totally f***ed up.
While this thread fell silent, the research & development continued... the svn trunk version of x64dtv has a new engine for DTVSID (based on reSID, with a lot of changes by Antti Lankila). The emulation is rather accurate, but there are still a few things to fix and/or figure out (are the oscillator bit trains 8b or 12b?)
The ChangeLog explains (some of) the SID - DTVSID differences, a proper writeup may appear eventually. The testprogs used can be found here.