For random pitch and delay there are two "JS" plugins I use:
IX_MIDI_Utils/MIDI_Tool - this has the random pitch controller
MIDI/midinoteondelay - This will randomly delay the note a given amount
The "IX" plugin may not be included in the REAPER install. To get it, go here:
http://www.cockos.com/forum/showthread.php?t=6632
As for the hanging note, there is a setting in Preferences>Audio>MDI Devices for "Send all-notes-off on stop/play"
Make sure that is checked off. If that doesn't solve the problem, try hitting stop several times, bypassing the VSTi and start/stopping, muting the track and start/stopping, etc... hopefully you'll find a way to stop it from hanging notes!
good luck with this