Good luck on your application. I went to Aoyama 10 years ago from WOU, (you know that smaller university 30min north of you)
I can answer some of you questions from above, though it's been a few months since you posted them.
About dorms, your only choice looks to be aobadai, but you do get a single room to yourself. When I went the men all stayed in Josei-ryo, which is old and has shared rooms/baths etc. But it was located right in Omotesando, so it was convenient. I don't think they put exchange students there anymore.
Also, Aoyama is known to be fashionable, so thus the women from that school are considered fashionable and attractive. It is not the highest ranked school, ranking status has a lot to do with Japanese peoples opinion of a university.
If you go there you will probably be in my friends Japanese class, she is the sensei not a student.
Good luck