Sounds to me like you've pretty much have substance in all the bases so my comments are mostly generic.
The length restriction of the presentation is probably going to require you to substantially trim down the scope of your speech. As fan, you are trying to include all the little elements of the topic that fascinate you -- but would swamp or bore a non-initiate. I'd pick a couple of examples to highlight - (e.g. Clannad (personal relationships), Higurashi (fantasy, mystery)) and simply note there's a vast array of settings and sub-genres to explore outside of those. You also haven't noted the RPG-visual novel genre ... like Utawarerumono which incorporates both visual novel elements and gaming action sequences).
Basically... scope creep will get you so be brutal in reduction. I made the mistake in 7th grade of trying to give a report on "World War Two". I gave it... it consumed half the class period and included a dozen posters. I got an A but my teacher and I had a long long conversation later about "control of scope" that stuck with me
