Font Editing in FR/LG/E
The reason that practically no FireRed/LeafGreen/Emerald hack has custom font is because practically nobody has found it. When you do have it, it's simple enough to edit:
Fire Red
Open your preferred version of Tile Molester and navigate to 0x1F3100. It doesn't look like anything, am I right? Well, go to View>Codec and select 2BPP Linear, reverse-order. There's one copy of your font... but mirrored. At the moment, you'll just have to flip it when you edit it, I can't find another way to do so. Each color font uses a different copy of the font image... Strange, huh? The other images are at 0x1FF300 for black, 0x20F618 for blue, and 0x21F930 for red.
They also have separate font width tables. These are what determine how wide each letter in pixels is. The tables are at 0x1FB100 for other, 0x207300 for black, 0x217618 for blue, and 0x227930 for red.