Homebrew PCBs

You *should* use the darkest setting your printer supports.  If the
toner spreads, you're probably melting it instead of just softening
it.  Try a lower heat setting.  You want the toner to stick to the
paper *without* melting.

For home-brew, I leave very little clearance around pins and such.
Maybe a few thou.  I use 13 thou drills for vias (unravel some 22
gauge stranded speaker wire), and usually 26 thou for pins (press
fit).  For regular pin/wire holes, 35 thou is the biggest I'll use
unless the pin requires bigger.

Don't include the component outlines.  Do those as a separate pass
after you etch, and just leave the toner on (black outlines).