1)I have passed emissions in Maryland (one of the strictest states) with a 350Z with an SC (also tuned by AAM)
2) I personally have no experience with the 370 Z but the internals have a reputation as quite good.
Much, much stronger than VQ35de (350Z)
(but then again u r running a lot of power, possibly at the max of what stock internals can handle... if it was me I'd downtune it a bit, but again I am not a 370Z but, former, 350Z guy.)
3) I cannot comment on price.. but from the mods list and from what I remember of AAMs price structure, I'd say off-the-cuff thats nearly $20,000 in quality parts and labor from AAM on the car.