Hi Dan,
Your settings are VERY slow for a Fiber laser. They’re actually in mm/min, not mm/sec as is common for this type of laser - galvo lasers can move VERY fast. The fact that you’re not getting a good etch with max power and minimum speed tells me there’s a high chance your focus is off. We have a new video going over the process: How To Focus A Galvo Laser - YouTube
First I would change from mm/min to mm/sec under “Edit > Settings”
Then I would try around 1000mm/sec with multiple passes
You may also want to turn off dot width adjustment, here’s an explanation of what that does - Dot width correction? - #7 by LightBurn
While etching a vector shape (as @albroswift mentioned above) does give you some more control, it’s not necessarily the reason you’re not getting a deep etch. If you’re etching a logo or text, it is certainly the way to go however. You can turn your image into a vector with the Trace Tool (Alt+T)