Thanks again for all the helpful data. So to your original question, the answer is yes, N1QL is aimed squarely at usage like yours. It should not degrade (except for the garbage-collection pauses you are seeing); it should support multiple clients (we will troubleshoot the multiple curl problem); and the client SDKs should work well as they mature towards GA.
Please lmk here if you run into other questions or observations.
Thanks,
Gerald