Park Tool has some great info about threadless headsets
http://www.parktool.com/repair/readhowto.asp?id=65
Threadless headsets are very easy and secure system. However, it does require the forks steerer tube to be cut to match the rider. Once cut, the only ways to adjust height are discussed above.
In your situation, it seems you cannot move your current stem any higher. But if needed, you can lower it by moving spacers from below the stem to above the stem (I think I see spacers below the stem in your photos).