8 is affinity, 9 is gender
AI values are a bit more refined than that. The actual mission the unit has is 0-99 (with only some of them coded, the numbers you mention) but the hundreds place is used for movement priority. So a unit with mission 1 and mission 101 will both do the same thing (attack in range), but the 101 will go first. That's why bosses are generally 500 or so, so they have an attack without moving mission and go before all the other enemies.
The final number in FACE_OFFSETS is the expression to use in the status screen
Con for generics can be set to -1 and it will use the class default (defined below the class generic stats)
The "Pre battle scene SKIP" event goes first because its trigger is Autorun. The SKIP part means that if you press ente- wait this is explained right on the second page
You can have multiple lines for the names of loaded text files but you'd have to do something like
I am 99% certain that \s[-1] is for the text box appearing at the top middle of the screen (for ghostly voices/echoes/from an unknown direction), but I think maybe I didn't code it right in FEXP? Either way \s[-2] is the one that you use for no text boxes at all
\r[#] can be used before a face sprite is loaded to make it load facing the other way (one of the houses in Tr2 used this)
For death quotes, \s will always be on the side the dying unit is on, instead of always being on the left
You missed a bit about external text usage, though I don't think it's used in FEXP. You can load multiple text files in a row to string them together, then play them as one conversation by using prep_text() instead of load_text(). This lets you fine tune bits of the conversation based on who is recruited/alive/etc, and other event related things. After you have all the text loaded in you have to use run_text() to make it play (load_text() is essentially prep_text() and run_text() as a single command).
Prf by character allows multiple people using commas as separators, just like Prf by class does (letting only princesses use some staff or whatever)
That's everything that jumps out at me