Inpainting(patch-based) only works for me in GIMP? Reproduction case included.

I apologize in advance if this is a stupid question, but I really don’t see what I’m doing wrong here.

Presently, I’m using G’MIC within GIMP to remove some credit-text from video frames. (Ah, the torments of making “abridged” series. :slight_smile:) I generate a mask for the instance of credit-text that matches how it looks over several frames, and I’d like to perform this removal as a batch job, but G’MIC seems to work completely differently from the command-line than it does in GIMP.

Here is a frame, and a mask, that demonstrate the problem.
My command line is:
gmic 0518.png mask-0496-0590-bw.png ‘-inpaint[0]’ ‘[1],7,16,0.1,1,1.2,0,0.05,10,1’ ‘-rm[1]’ -o 0518-inpainted.png

The parameters match what I see in the filter-dialog in GIMP.
However, my mask in GIMP has a red foreground and a transparent background, and I have to flatten the image before I can perform inpainting; I’m not sure the G’MIC filter in GIMP works any other way. But the gmic command-line tools doesn’t work at all with a red/transparent mask, but does something (not much) with a mask with a white foreground and black background.

This is with version 2.7.0 of gmic, as packaged by Fedora Core 31.

And since I have your attention, I have 3 other questions that might be in the manual, but I’ve been unable to find them.
[1] Is there a command-line equivalent to the “mask color” option GIMP displays in the G’MIC inpainting(patch-based) dialog?
[2] Is there a command-line equivalent to the “mask dilation” option GIMP displays in the G’MIC inpainting(patch-based) dialog?
[3] Is there a way to apply a selection-rectangle while doing inpainting from the gmic command-line? Some of my inpainting worked much better when the active area was limited in this way (to avoid pulling in nearby things that didn’t match the area being inpainted).

Thanks in advance for any clarifications!