Not coming across as a jerk at all. These are totally valid questions.
If you come at it from Lar's perspective, he was 7 when it all went down. He doesn't know any better. It's not in wheel house to assume his parents could/would lie about this. They have him cut off from the rest of the world, sheltered, so all he knows is what they tell him.
Regarding Loren still being friends with the gang. Well, Loren' ran away' from his family, a family that had made him feel like crap. So it's not unreasonable that Loren would go back to his friends while not going back to the family.
ETA: Loren and crew started filming when they were 13ish? so that's still 6 years after he ran away. That is a long time to circle back to his friends