I did a walk through video for the calibration and alignment, and that talks about a number of things you mention (card angle relative to the camera, best camera placement, etc).
A couple other things to check:
- Camera is in focus
- Lighting is relatively consistent (lots of these have auto-exposure)
- Calibration card is very flat
- Capture is at high resolution, not 640 x 480
A 170 degree camera is going to be harder to calibrate, particularly at the edges of the image. If you have to bring the card inward, away from the edge of the image to get a good capture, do so. The code is measuring the curvature of the lens, and with extreme fisheye, there’s so much distortion at the edges that it can be hard for the code to find the dot pattern. The lens curvature is consistent across the lens, so it’s OK to move in a bit.