1&4) We've at least identified a problem, and it's now in the capable hands of our programming team.
2&3) Plogue Sforzando is not a General MIDI plugin, nor is it multitimbral. It is not capable of playing more than one instrument at a time, unless you use a separate instance of the plugin for each track - most instrument plugins work this way. CoyoteWT and Cakewalk TTS-1 are both General MIDI and multitimbral, so they are both capable of working in the way you are expecting them to.
Wow, Thanks ! Will it be fixed in an update ?
Thanks for clearing out on Sfzando :-)