#1, we dont need to know where your card stands. 3dMark is probably the most innacurate benchmark ever. The companies can optimize for it, and it doesn't accurately represent real gaming performance. For instance the Geforce FX series always beat the Radeons in 3dMark. However in games the Radeons slaughtered the FX's.
#2, how do you know 545 isn't stable. Have you ran through some real games with it. If/When you do that, if there are artifacts it is unstable. If not it is, obviously, fine.
#3, test doesn't change the clocks. Test merely tests those settings. You select the settings hit test, and then apply those changes.
Finally, if you are so hellbent on OCing this poor card, then in Riva Tuner there is an option to manually input clockspeeds (any clockspeeds). I haven't used it in a ~year so i cannot remember exactly where it is.
-Kevin
Oh yeah, it may not be changing because it is a mobile chip, and keeps throttling down everytime you change it since you are not in a 3d application.