So I have been following this thread for a while and I have finally decided to register here and post something.
First of all, thanks to Zerea for the move data spreadsheet, I've been trying to figure out the meaning of the unknown values for some time, and the data has been really useful to me.
Now I will share my findings:
Bitfield 2 Controls the way enemies use moves. It works the same way as bitfield 1: If a move has a value of 48, enemies will use it if there's a party member in the same room.
You can try and give a value of 48 to some move like Tackle, enemies will try to hit you from far away (and obviously fail)
For some reason certain moves have different values for bitfield 1 and 2 when they should be the same, for example Discharge has Bitfield 1 = 48 and Bitfield 2 = 64. Although it is a move which hits all enemies in the room, other pokemon will only try to attack you with it if you are up to 2 tiles away from them.
Enemies (and I guess allies too) use the Unk6 value of a move as some sort of "weight". The larger this number is, the greater is the chance of a pokemon using it. A large value here means enemies will use the move constantly, and setting this to 0 causes pokemon not to use that specific move at all.
Unk7 is that other accuracy value you were talking about. If the move misses due to this second accuracy, a different message appears (I think it's 'the move missed X' instead of 'the move failed to impact X')
Unk10 is the number of times a move hits. 0 means it hits a random amount of times.
Unk13 = 1 means the move is affected by Magic Coat
Unk14 = 1 means the move is affected by Snatch
If a move has an Unk15 value of 1, it can't be used under the muzzled status (caused by a silence orb). That's why biting moves all have Unk15 = 1
Unk17 = 1 means the move can be used while taunted
Unk19 controls the message that comes up when the move is used. A value of 0 means default message, 1 would be the next string in the game ('Oh no! (Pokemon) chose (move)!') 2 = Regular attack message, and so on
Orb-effect moves are easy to test, I just make a quicksave in a dungeon, edit the save file and add those moves to the team leader or the enemies:
Famish: Decerases by 10 points the belly of all enemies in the room. Enemies/party members will act the same way as if they had eaten a hunger seed once they get affected 10 times by this move.
Observer: Foe-Seal orb.
Possess: Probably has something to do with the 'Possess Orb' from Mystery Dungeon 1. Using the move does nothing.
Searchlight: Has the same effect as the luminous orb.
Siesta: Same effect as the slumber orb.
I hope that helped. Sorry if I made any grammar mistakes, English is not my first language.
PS: @psy_commando, the sprite editor crashes for me every time I try to import/export sprite palletes (no matter if I save/load it as .txt or .pal). I don't have a github account to open an issue so I post it here.