My DS4 is big-time into asking me questions he already knows some or all of the answer to. When he asks me that sort of question I respond with, "Well, what do you think?" and usually he will tell me whatever's been spinning in his head.
I hope you have a productive meeting with the school, but if they don't have some good ideas about why his IQ scores have such vast variances, I would certainly seek out a specialist who can help you figure it out. With some scores at 99.9% and some at 50%, the full scale IQ probably isn't a true measure of his intelligence, and it would benefit him to find out if a learning disability it at play and what to do about it.
If your husband is trying to get your son to think he knows everything then he's both foolish and mean. Does he allow your son to be rude to him? Does he allow him to be rude to you? Do you and your husband both talk to your son in your native language?
This is not a question of intelligence, it's a parenting question. Is it normal in your culture to allow kids to treat adults like this?
These questions occurred to me, too. It is not healthy or wise for anyone in the family to allow one parent to be set up as "the smart one" and more worthy of respect. So I hope that's not the case. It's hard to tell from a post on a forum like this so maybe I am reading too much into it, but respect must be given by all parties in the family.
