ORIGINAL: behemas

Hey guys, im pretty new with all the electric stuff, but need to sort out a couple of things. I've got a Turnigy TrackStar 1/8th Sensored Brushless 2100KV motor with the following specs:
RPM/v: 2100kv
Max voltage: 15V (4S)
Max Current: 140A
Max Watts: 2100W
From these numbers i'm able to calculate the torque at the shaft provided at max RPMS, using 4S battery. Torque=Power/Angular speed, angular speed being 2100kv*15V/60*2pi= 3297 rad/s
Torque=2100/3297=0.637Nm
Now my questions:
1. What is the relationship of rpms and torque in rc brushless motors? Do I get larger torque on my motor at lower revolutions (controlled by esc)? The vendor doesn't provide any speed/torque curves, is there a way I could do some theorical calculations of the torque provided at different revs?
2. If I was using 3s battery, which makes 12.6 volts at most, my max RPM would be 26460. Max power at this voltage is P=UI=12.6*140=1764W, right? so my maximum torque T=1764/2770=0.633 should remain the same. That brings it back to the first question - if the ESC controlled the voltage provided to the motor only, it would mean that torque is always the same, but is that true or not?
3. A different question now - how to determine motor acceleration time to the max revs? I guess its not possible to calculate the acceleration time to max revs when the motor is subject to some load? Its possible to get the startup time lower, by adjusting ESC ''punch control'', however it is not adjusted by seconds, and I need to know the realistic acceleration time, anyone could offer a good approximation with a ''soft'' setting?
Thanks!