It sounds like you missed nearly all of the steps.
Good luck with the root canal.
From your description it doesn’t sound like you did anything as I described it.
Don’t adjust the transparency of the imported texture in SketchUp. That will make transparent the areas you want to keep as opaque, too. Don’t use a screen capture application to create the image from SketchUp.
Use SketchUp’s export feature to make the image. Save it as a PNG with transparent background (set in the export options) and then crop the image in an image editor. Here I’ve done this again with a different pattern this one has a face for the pattern instead of just being edges but the process is otherwise the same.
PNG as exported from SketchUp.
After cropping to the pattern. Note that as shown in the image above, I added a border around the extents of the pattern to make it easier to crop to the pattern.
The areas that show as white in those images are transparent.
After importing the image, above, as a texture, there’s no muddiness in the texture.
