Those results look about what I would expect if you haven't implemented vid_get_viewport_live_fb()
A couple notes
1) md_tune only produces valid results if the AF lamp is the only thing triggering MD. If there is triggering from e.g. garbage in the unused parts of the buffers, noise, other motion in the scene, then the results are meaningless. The junk on the right side of the screenshot suggests this cam may suffer the same false triggering problems as g7x (this may only happen if you do implement vid_get_viewport_live_fb)
2) running chdkptp live view might impact performance, since transferring a frame takes significant time. (it might not though, since it happens in a different task is probably done mostly outside of the main CPU)