Ubuntu :: Simple Small Text Editor 3 Features

I am looking for an editor to fill a specific request for a mostly non-computer person. He uses a computer to write manuals and other books for classes he teaches. He has come to ubuntu so he can more easily access updates, gimp, etc. than he felt he could in Windows.

1) I need a text editor that can be kept open without bogging things down, or can be loaded fast enough to make him think it is "TSR" (made usable in either case by a keypress on his MS internet antique keyboard)

2) Spell check as you type with editable dictionary (he can add words that will no longer show as incorrect). Ability to select spelling suggestions easily (left click a misspelled word is his current method).

3) Ability to highlight words that most of us would call syntax highlighting but for words having NOTHING to do with a programming language etc. I would call it ability to edit the keyword file(s) to make his own languages to be highlighted.

Already rejected:
* anything with millions of complex keys to @#%$^%#$ remember that don't make sense
* gedit
* geany
* kate
* openoffice
* treeline (though he does use it for other things)
* tomboy (the cuss words there are an art form)
* anything emacs/vi or similar (see #1 reject reason at top)
* some gtk-nano clone he has no idea where he found