Scroll bars are not proportional in the symbol editor as you state, it is a known issue.
Also, pan and zoom in the symbol editor is the same as in Expedition PCB (rather than PADS - also a known enhancement request). So to zoom use the scroll wheel on your mouse, roll forward to zoom in, roll back to zoom out, to pan press the middle mouse button/scroll-wheel and move the mouse in the direction you want to pan.
This non-standard mouse behavior is extremely frustrating. When will the "normal" behavior be available!
Gordon "Opinions are my own"
Only non-standard if your a PADS user :-) Anyway, we will be changing this in a future release, but it is some way off, so not the next PADS release.