Find camera pose by knowing triangle coordinates
No.  No.  You can't.
Not completely at least.  With only three points, the math has two solutions.  Your triangle could be tilted in one of two positions.  Like picking a square root.
From a single frame, you might be able to tell and measure motion from a blur gradient, but that is difficult.
From multiple frames, calculating the position of the camera for each frame, the velocity is simply a matter of differentiation techniques on a finite sequence.