This is a really exciting concept and I would be very interested in the results of your survey. However, care must be taken so as to not misinterpret the results.
For example, the aggressive-or-not word association is also dependent on a gamer's general entertainment profile, which includes movies, books and other concept-intake methods. Especially the example of "kiss-kill" made me think that the standard male of age 18-38 will probably write "kill" rather than "kiss", for many social causes other than gaming (e.g., gender stereotypes). I am certain you have ways to account for that, but I thought I should point it out :)
With respect to the game, although the FPS part is rather concrete for the purposes of your study, I am concerned whether it might be a little to "abstract" to actually cause the ammount of immersion you might need for a direct psychological impact. This is, of course, also dependent on the player, so I suppose you can control for that by using the questionaire in the beggining, but a few more questions might be in order. For example, I am not used in playing FPS games, so I probably got more "anxious" than a player of my age that mainly plays FPS games, so a question related to the game genre of choice might be in order (unless you can infer it from the rest of the results).
I was very happy to see this attempt and hope your research gives you some insights!