Safety height isn’t super critical, anything greater than zero will probably be fine. I usually do .25 inches. Step down should be around half the width of your router bit so if you are using a .25 inch router bit a step down of .125 is about right. Feedrate is limited to 40 inches/minute and I usually run at 40ipm. The plunge rate really doesn’t matter because again it will be limited by the hardware moving speed. I’m not sure I’ve ever actually messed with that one.
The easiest way to do this is to generate two gcode files, one for the v bit and one for the edge cut. As long as you don’t press the “Define Home” button between cuts they will stay aligned.
I found that for circles small enough for this to be hard it is usually safe to have no tabs. The part that gets cut out usually gets sucked up into the dust collector without issue. I have had it bounce around in there and cause problems, but that is rare.
I haven’t used freecad much, but I’m betting there is a font. You could also look at a more sign making specific program like Adobe Illustrator or Inkscape which would have lots of fonts
This can be tricky because it has a tenancy to melt. I haven’t done it personally, but I know there are special router bits specifically for this kind of thing. Maybe someone with more experience can jump in?