> I [...] would like the popups to respond keyboard (Tab) focus changes as well as mouse movement focus changes.

Should tooltips also be shown automatically when the keyboard focus is on a widget?  Using the same delay as for the mouse hover, perhaps?  I've never seen this in another app that I can recall.

If so, should it be possible for two tooltips to be shown at once, one for the mouse hover and one for the keyboard focus?

If keyboard activation is desired, perhaps we should have a keyboard shortcut for that?  We could use the one currently used for showing calltips in the editor.  Is there a standard/convention for this on any/all OS?