What tool is used to edit these types of files, *.big?? For example the 'real gamplay patch' what tool did you use??

.big? simple! EA graph , since you are clearly very new; here's the full name ( ;) ) : EA Graphics editor, it can open .big, .fsh .. etc...
:)

Do anyone knows if there's a file I can download, or an article that explains many of the settings contained in the ini.big file?
For example (i would like to know what changes these settings refer to, in the game):

// Save determination
SAVE_SPEED_WEIGHT = 100
SAVE_TRAVEL_WEIGHT = 10
SAVE_SKILL_WEIGHT = 50
SAVE_DEFENCE_WEIGHT = 200
SAVE_ATTACK_WEIGHT = 200
SAVE_RANDOM_WEIGHT = 5

EVALBALL_BESTCASEDELAY = 0
EVALBALL_WORSTCASEDELAY = 40
EVALBALL_BESTCASESPEED = 9.0
EVALBALL_WORSTCASESPEED = 7.0
EVALBALL_MAX_PLAYABLE_HEIGHT = 10

and so on... plz help me someone?

not new but haven't had the need to edit gameplay til now just needed an refreshment of info.. thanks for the reply