Id say 1qt/1000mi is pretty bad.....
There is no reason to lose faith! You can always do a leak-down test to confirm if the oil is getting past the piston (blow by) which would then essentially lower your compression. We build a lot of STi motors as piston #4 is a common failure point. A ring issue is the most obvious thing to check for oil consumption, just not typically with such low milage. During the leakdown test you will bring the engine to top dead center and make sure the camshafts are in the correct phase. You want intake and exhaust valves closed, and piston at the top of the deck. Then use your leakdown test to force compressed air (typically ~90PSI) through the engine. It will then give you a % of leakage. If you hear it out the intake or exhaust you have a valve train issue, if you feel air or hear air out the oil filler neck that is a piston issue, if it comes out the radiator cap then you have a head gasket issue. I think if you can find a reputable shop to perform the test, then if you had poor results you could go back to Nissan and present your data to help with the warranty claim.
Thanks,
Alex Goodwin
AlexG@motionlabtuning.com