The progress on the buffet table goes as follows:
Y multiplied by 25- where Y is number of days where you used buffet.
So on the 5th day you will receive 125 Theon points :)
Only on 7th day this will change, and you will receive 300 points.
|8th (1st day of new streak week)||25|
Your streak will not break if you skip one day.
Additionally maximum streak is 7 days, as confirmed by Skerio:
it would be a shame resetting the streak and starting from 25 theons in the middle of the event with no possible way to avoid that.
It should be noted that the maximum streak is 7 days, after which it begins at day 1 again.