like i said, if youre doin it right you should be gassed by the end of your session. did you read the book or just find the routine?
every set is to failure. remember youre supposed to stay in the prescribed rep range. so on your endurance days, if you squat 3 sets to failure in 13-15 range, you should be limping home. week 2 is worse and week three is terrible.
do the program as is. it was built like that for a reason. what are your exercises? are most of your exercises from level 6 and 7?