APS Ethos will often open an AutoCAD 2000 dwg, the set colours are preserved.

Make sure all coordinates in your drawing are positive, i.e. in the top right quadrant from the User Coordinate System (UCS) icon.
Seen in the bottom left corner of this screen shot.

Make a copy of your drawings and scale to the required model size.

Create a new layer for the laser cutter path and use polylines to trace just the cutting paths or use join and the Overkill command.

Or in Ethos: Select Common Line Removal from the Outlines menu.

Laser cutting can be made more efficient by using the Re-Order Cut Path command from the Outlines menu.