7 is just popular. 7 pieces of soul, 7 years attendence, 7 members per team, 7 floors in castle, jkr liked 7.
The map obviously is tied into the castle wards. It scans and tracks which seems fairly basic, but tying it to Hogwarts seems VERY unlikely for mere students.
Luna without a doubt for dating, but I wouldn't say no to Tonks either.
Would save Tonks she is so much fun and is wasted on a self hating pessimist like Remus.
Favorite characters. 1. Luna 2. Tonks 3. Dobby. Honorable mention to Mad-Eye Moody.