Without upload files or screen images, we're guessing here, so if yuo can provide these, your replies should improve.
That said, I'm not in front of SolidWorks at the moment, so please bear with me.
In your second attempt, was the assembly view placed outside of the drawing border? (Whether or not there were title block elements remaining doesn't matter.)
If the view was outside of the border, and you had deleted the title block elements, then I believe SW didn't have anything to export.
I'm assuming the DXF save as is similar to a drawing save as to another format, such as a PDF.
Anything outside of the border is automatically excluded,
Trying moving the assembly view to where the drawing border was (or enlarge the drawing size).
Also, you don't have to delete the title block elements before the DXF save as.
You can open the DXF in DraftSight afterwards and delete them there.
I'd recommand opening the DXF in DraftSight regardless just to be sure the DXF files was created as you require.
I hope this helps.