Okay, I don’t have AutoCAD, but what you need to do in that program is create narrow rectangles the same width as the stroke lines that you are using, give them a Fill color but no Stroke or Outline color.
Engraving always happens on closed filled (vector) shapes. Strokes always default to Cut lines, and although the Glowforge interface can convert them to engraves, it might not interpret them correctly. (Which is probably what you are seeing.)
Your other option is to rasterize the engraves. Use a high DPI (>300 dpi) and the things that you want to be engraved will look identical to a vector engrave. The raster image will need to be combined with any vector cutlines in another program like Illustrator or Inkscape, but it is a quick method for making a combination SVG file.
If you can export a jpg or png from Autocad, that’s an easy way to turn it into a raster image. (Hide the actual cut lines first, I assume those will be a different color.)