I found an interesting site where the hidden book of St Thomas is found. The site is www.earlychristianwritings.com/thomas/ . There, you can find all 114 verses in that book, in three different versions, and user comments about the subject.
What I have noticed was more of a seek and you shall find theme. There is little in the way of repenting for your sins there. Some of the verses closely parallel other scriptures, and there are parables similar to those found in the other Gospels. What you might notice are some of the user comments. And a lot of it can be applied in ways that have nothing to do with the Watchtower Society, or even in religion.
One thing I noticed was the reference to "fasting as to the world". Taken literally, this might seem to parallel the Watchtower Society's take on the subject. However, what I got out of that was that we ought not let the world's leaders try to dictate what we ought to think and do. Independent thinking is highly suggested, and people that learn to think on their own are actually following this message against letting the world do the thinking for you. There are many other ways to interpret the passages, and I do encourage reading the other comments and even adding any you may have yourself.