How to play a Grandmaster in a simultaneous? Would you play well known Opening theory, or avoid it? What other strategies would you employ to beat a GM in a simultaneous? I have my own strategies which I've used. See link in my profile. But what is best?
I've answered a very similar question here

My take is that GM try to avoid calculating, and try to rely on their superior positional understanding. So striving for a tactical position, seems like a good bet. Your game seems to support this hypothesis.

Here is interesting story, that involved somebody I used to know over the internet and Kasparov:


  [Kasparov] rather nervously asked me if I had a rating. I replied 2084 and he, not looking very happy, asked why I didn't write it down in front of the board next to my name. I replied that no one asked me too and that the Belzberg people knew my rating and only today OK my playing since I am a client. He then stated that if he had known I was rated that highly he would have played differently rather than getting into a very theoretical line. Being aware of the 2000 cutoff I again appologized for the misunderstanding and we quickly realized that the Belzberg staff had erred in not telling people to write down their ratings (these were different people than from the NYC event). I simply stated "I'm sorry for the confusion, I won't play" and started to get up and Garry, reiterating that he'd have played differently vs a rated expert, started resetting the pieces to the starting position and said we can restart. Being rather shocked by this and what was over a minute of commotion and confusion I knew the gentlemanly thing for me to do was to step away and let someone else under 2000 play.


source

The position was a very sharp double-edged Scandinavian. Something even Kasparov wouldn't want to play against a high-rated player.