sounds like you just need some elbow grease and patience.
just dont twist your bars to the left because the compression will loosen and the shim will come off into your bars, giving you a bigger problem hahah
since there is a lip on the bottom of the shim try prying the bars from said lip. Work your way around the whole thing and voila.
Doesnt work. I Tightened the headset all the way and i tryed to put the bars over the shim but it wouldnt go on easy so i took it outside did a couple of ollies and the bars went all the way down but the headset got loose again and the bars wont come off