#1. JW`s, the r&f have to rely on the interpretation the Governing body puts on scriptures ,they don`t beleive you can read the Bible on your own without them to get the true meaning conveyed in the Bible.
#2. This all relates to how you / they interpret the bible passages in question
#3. Do Jehovah's Witnesses have assurance of salvation?
No they don`t , and this also relates to how they interpret the bible passages in question.
To answer your 3 questions in one sweep is to understand the JW religion is a dictatorial religion ,it is our way or the highway ,if you don`t agree with the GB to the letter ,you wont be accepted as a practicing Jehovah`s Witness.