Have you actually made "il" "li" and "ll" tiles in the ROM? they don't exist by default, so you have to get a graphics editor (Tile Layer, Tile Molestor, and YY-CHR are the moist popular AFAIK), find the game's alphabet, then use one of the blank tiles in that bank (there are a lot, because they blanked out all the kana from the JP version).
There's more steps after that, but let's start there - have you done that yet?
I just remembered that you used PII as the base for Ultima, so the tiles should already exist.
OK, so next, you'll have to edit FF4kster's config file so that the program knows how to enter one of those tiles. In order to do that, you'll need to know the tile IDs of "il" "li" and "ll." Easiest way to do that is to get a graphics editing program (any of the ones mentioned above - I use Tile Layer personally), load your ROM up, and locate the font.
In the menu: View>Format>Game Boy
Then, hit Page Down until you see the font (and other characters/symbols). If your ROM has a header, it'll be at offset 057200.
Note the location of the tiles relative to the other font tiles. They're probably immediately after the numeral 9.
Then, in FF4kster's subfolder "config," open "font.dat" in a text editing program (notepad, or whatever). Scroll thjroigh the file until you see the character that immediately precedes ll, il, and li. Note the hex value assigned to that character (if the character is 9, the value will be 89). The characters you want to assign in FF4kster have the next three consecutive hex values (if they're after 89, then those values are 8A, 8B and 8C).
Then, simply edit the config file to include entries for il, li, and ll. I'm not sure, honestly, if the config file will recognize two-character entries, so you may have to enter them as unused characters, like "(" ")" and "*." Once you've edited the config file, save changes and exit.
Now, when you edit text in FF4kster, when you type whatever character you assigned to those tiles, the program will insert that character into the text. FF4kster draws from the actual ROM's font, so you'll see "ll," not "*." So you will know immediately upon editing text if you've done it correctly.
Hope that helps!