About slowing tempos: in the pre-X versions of Sonar (and in Cakewalk) there were a set of "tempo scale" buttons. Button 1 decreased the tempo by 50%, Button 3 increased the tempo by 200%, and Button 2 returned to the original tempo. These were extremely useful for recording complex MIDI passages without fooling with the tempo map.
Unfortunately the Bakers removed this feature from the X series. I, and others, have asked that it be restored but to no avail. (There was one glitch in the feature: it wouldn't work as soon as any audio tracks were added.)
I've been forced to use a work-around when working with multiple tempo changes in large works: I cut the tempo information to a new file, save it, then reset the tempo in the original. After recording the tricky parts, I copy and paste the original tempo info back into the file. It's not as elegant as the scale buttons, but it works.