I would provide the wiiki that shows your error but it is the same source you are using. It's not worth the time and numerous arguments to explain it to you.
Let's finish your example
200 members
OLD: (200+10) * 845.028800 (L76) = 177,456
NEW: (10+10) * 845.028800 (L76) = 16,900
Difference = 160,566 Less in new per day. Prior to the change the daily decay/member was roughly the same as a guild of 5 and now after the change it is reduced by over 90% for the guild of 200.