Hmmmn…okay, first off, anything you want to engrave, you will want to leave as a bitmap. (Don’t trace it first. The Glowforge does a fine job with bitmap engraves.)
This is what your Trace actually looks like when you remove the fill color - it’s going to burn along each of those lines, and some of them are too close together.
Having said that, it wasn’t a waste of time since you can maybe use the trace results to cut out the lake. You will need to separate the lake body from the tributaries using the editing tools in Inkscape, but that’s a good trace result, so it will cut out the lake pretty well.
I would delete everything except the lake from that trace, leave those cutlines in there (which means setting a stroke color and removing the fill color for the lake, just like I did with the picture above), then drag in another copy of the original bitmap and align the lake in the bitmap with the lake cutlines. Then draw an unfilled rectangle around the whole thing to cut out the map. (I don’t remember if Inkscape destroys the original bitmap that you used to trace with, if it’s still in there, you can use that one.)
Not exactly beginner level, but not too terribly difficult either. Should be a good little project.