Maybe. But I think there are some disputed texts in the JW canon.
Rare, but you are correct. However, my favorite Bible translation alerts the reader when manuscripts are variant. A good example is Psalms 82:1 -
Much more common in the NT than the OT, I think. Maybe because we have more of the NT to compare.
Is it hard to know what to believe if you don't really know what God or Jesus said and did? Or does it even matter, faith is a better guide anyway?
Faith without accurate knowledge is blind faith. The Bible directs us to "Prove all things" (1 Thessalonians 5:21 KJV). In the definition of faith in Hebrews 11:1 the Greek words used involve "evident demonstration" and "convincing evidence." Blind faith is not an accurate guide but faith based on accurate knowledge is (John 17:3,17).
If Jesus did not quote Psalms 82:6 at John 10:34-36 (from the LXX btw) then who did?
There is another example of corruption of Scripture - one that occurs about 7,000 times in Scripture! It is the removal of the Divine Name. For example, the greatest commandment in the Bible according to Jesus is at Deuteronomy 6:4,5 which Jesus would have quoted accurately (Matthew 22:37-40). Mark records Jesus' quote more extensively here:
Mark 12:28-34
One of the scribes who had come up and heard them disputing, knowing that he had answered them in a fine way, asked him: “Which commandment is first
* of all?”
+ 29 Jesus answered: “The first is, ‘Hear, O Israel, Jehovah our God is one Jehovah,
30 and you must love Jehovah your God with your whole heart and with your whole soul and with your whole mind and with your whole strength.’
+ 31 The second is this, ‘You must love your neighbor as yourself.’
+ There is no other commandment greater than these.”
32 The scribe said to him: “Teacher, you spoke well, in line with truth, ‘He is One, and there is no other besides him’;
+ 33 and to love him with one’s whole heart, with one’s whole understanding, and with one’s whole strength and to love one’s neighbor as oneself is worth far more than all the whole burnt offerings and sacrifices.”
+ 34 At this Jesus, discerning that he had answered intelligently, said to him: “You are not far from the Kingdom of God.” But no one had the courage to question him anymore.
+
The original Hebrew text for Deuteronomy 6:4,5 which Jesus is accurately quoting has the Divine Name 3 times. However, most Bible translations remove that name (Hebrew H3068/Yehovah) and insert "Lord" (Hebrew H113/adon; H136/adonay (emphatic) and Greek kyrios/Lord - and do this about 7,000 times!
One might ask, though, who removed the Divine Name from the greatest commandment in the Bible (according to Jesus)? There is evidence. For example: LXX (Greek Septuagint) retained the Divine Name until after Jesus' time - we know this from manuscript copies of LXX from before and during Jesus' time. But by the time of Origen's Hexapla, some Greek translations had removed the Divine Name and replaced it with Greek kyrios/Lord - that would be the late 2nd century CE.
Who removed the Divine Name is an interesting study subject. It is noteworthy that only God's name was removed - not other personal names - not even the names of false gods were removed!
But there is plenty of evidence that the Divine Name is found 3 times in Deuteronomy 6:4,5!