You might want to reconsider using RxJS on backend, since it is significantly slower than Bluebird promises (which you should be using instead of native V8 promises at least for now) http://bluebirdjs.com/docs/benchmarks.html
Yep. Time tracking software is quite good at proving this. When one becomes disciplined in tracking "focused work", it becomes obvious that these mythical 60-100 hour work weeks are nonsense.
It might be long enough for some, but not the others. Startups need to have majority of things right even before getting into YC and then improve more under YC mentoring.