Thanks!
I was able to restore Fn function! I followed the instructions from your posts (and from the referenced posts) and now the Fn key works.

What I did:
1. Started xterm
2. Gained root access: "sudo gainroot"
3. Started emelFM2 from xterm: "emelfm2"
4. Looked for "/etc/init.d/x-server" in emelFM2
5. Highlighted the x-server file in emelFM2
6. Hit the "edit" button in emelFM2 (the one with a paper and pencil icon)
7. Found the offending line near the top of x-server:
ARGS="-mouse tslib -nozap -dpi $DISPLAY_DPI -wr -nolisten tcp -extension XInputExtension"
8. removed "-extension XinputExtension" with the backspace key to leave the correct argument:
ARGS="-mouse tslib -nozap -dpi $DISPLAY_DPI -wr -nolisten tcp"
9. Hit the "Save" button, then "Close" button.
10. Exited all apps and then rebooted
11. Tested the Fn key and it worked!

Thank you all! It looks like I can put off wiping my SD card installation for another day!