1. Nothing to be concerned about. Keeping an eye on the oil is the only thing you really need to watch. It doesnt really burn any, but that leads to you never checking it which is where most problems with VQ engines come in - oil starvation. Its the only real problem I've heard of with VQ engines. The one in my 350z when for 99k miles with no problems when I traded it in for the '70.
2. This is down to driving style but anywhere from 30k miles onwared. Mine on the 350z lasted til 72k miles. Have the 7AT on the 370z so no clutch for me, but I'd expect it to be the same as the 350z.
3. I do a mix of driving and with some motorway I see ~28MPG. With more town driving that usually sits around 26/27MPG.
4. Nissan paint is fairly thin so chips easily. Other than that though, theres no real problems. Nissan still havent learnt to be able to match paint between panels, but its usually only obvious on camera. No different to most other manufacturers bar the Germans.