1. The only Addict currently in stock is the 52100 (carbon steel) version. It would be considered a fairly standard gyuto shape....not overly flat or over bellied.
2. Yes, to some degree....but in my home I don't draw huge preference for one design over the other as it pertains to profile. I have, and use, both narrow and wide gyuto's.
3. The Addict's that are made by Lamson (I swear I remember one made by Konosuke but can't find it right now) will not be as thin as the Shun.
4. Depends on which Addict you're talking about. The AEB-L and 52100 versions will take the sharpest edges....the CPM154 version will hold an edge better in theory (I am a home cook, so testing edge retention is not so easy for me to do...but CPM154 should keep an edge longer than the other two).
5. People are generally referring to overall thickness....not just the spine measurements. Having never seen the JKI knife you mentioned, I can't comment specifically though.
If I were you, wanting a stainless laser...I'd up my budget a bit and get:http://www.chefknivestogo.com/laser.html