I might be able to explain the power meter, but not much else. The meter is going to show an average power, because it does not react very fast. If you get a constant pulse per step, the faster the steps come the higher the average power. That is one part of pulse method that works. You do not need to compensate for speed during acceleration. It will naturally up the power at higher speed.
In theory, you want the Mach3 plugin to get multiple steps per pixel. It can then create an on/off pattern of pulses to simulate a gray, like a laser printer creates a gray. If you have 1 bit depth, it does not matter, but more pulses per unit of length is always better if your image is light. It is still like painting with a paint ball gun, but that is the best Mach is going to do.
My problem with the pulse method is if you have an all black image you should be able to peg the meter. The laser should stay on and not go off.
You have a retrofitted commercial Chinese machine right? What was the factory steps per inch? What is the model number?
"If you didn't build it, you will never own it."