Is there any way I can gauge my IT knowledge to better help me find where I am weakest and strongest to get a higher end position?

I am stuck as the "IT Guy" in small businesses.  I apply at higher level positions in large corporations and am asked questions on problems I have not encountered in my 8+ years of experience.  I have never seemed to have a problem with my background on getting to (sometimes multiple) interviews.  I want to move up in my career and know I require more training and studying, but I can't afford to not work full time nor waste money on classes that will not help me develop.

I am wondering if anyone knows of any sort of all encompassing IT IQ tests, if there are frequent meet ups for IT professionals here in Orange County, California, or if someone in a Senior Windows Systems Administrator (or similar) position would be willing to evaluate my knowledge to help point me in the direction I need to go to gain the knowledge required for such a position.  I do have quite a bit of experience with many different environments, but when asked some questions in interviews, "Well I'm not sure of that, but I can figure out how, quickly, when faced with it," is not good enough.  For example, I can and have had to seize FSMO roles from dead Domain Controllers, but can't tell you off the top of my head what the exact ntdsutil command is without looking it up using help or Google.

Any advice is much appreciated.