My way works for me.
Do you use a Style that has Profiles set [say at 2] for the current exported scene [I think you must have, as the dialog's option ought to be 'grayed-out' otherwise ?].
Also why aren't you exporting Full-Size [1:1] - I can't see any logic in other ratios - you model in the SKP and in a DWG with 1 file-unit == 1 world-unit [in 'model-space' at least].
My profile's polyline thickness is set to a few mm, BUT it's overridden by 'auto' being checked anyway.
On a MAC you don't seem to have 'version' choices for the DWG file's format
These are the only differences I can see...
If you mimic my settings as near as you can do you get any improvement? ...