N. hamata is fairly slow growing. That really nice specimen you may have seen is at least 5 years old. Humidity is important to a small plant. Just partially covering it with a clear cup can do the job. Leave some opening, however, or it will be really difficult to harden it off. Older plants handle lower humidity better. Also, it's best to find a partly sunny location, such as your west window, and leave it. Moving plants around from location to location is always a bad thing since they never have a chance to adapt to the microclimate. With a more challenging species you need to give them time.