Oh, the glorious Christmas gift of ENTERTAINMENT! ClarkFan1979, so sorry you had to be the conduit for this pile of chuckles. At least he is giving to you, not (so far) trying to get you to buy his wares, as so often happens in MLMs. In my own mind, I will classify him as Kindhearted Bro until further notice.
Re your questions:
1. Of course you can tell him, but why rain on his parade? He is not going to learn from you, only from experience, if at all. He will, however, feel the love or disdain in your response. Tell him you admire his bold spirit, and ask him if he's going to take you to Acapulco or Dubai when his dinars revalue.
2. See 1.
3. I was wondering that myself. I can only assume they sell above the exchange rate, or sell counterfeits, or sell the old notes that have been replaced by new ones when the Iraqi government lopped three zeroes off a few years ago (I read that Forbes article). Best guess: selling the valueless old notes at the price of the new notes. Great margins, plus they can appear to be giving zero markup.
4. Exchange it for Bitcoin! Bwahaha, my whole response was just to make this one brief joke.
Quiet times here, hope this offered a shred of amusement. In all seriousness, I once had a friend whose financial schemes ranged from wild failure to just being broke on a regular basis. The choice was to enjoy to his merry ways at the price of observing his failures, or block him off and wonder what was happening. I chose to enjoy his merry ways. Even more so, a relative is someone you don't want to block off unless staying connected is actively harmful. Good luck getting rid of the bills or coins. And having lost a relative or two in recent year, treasure your brother for who he is, even if it's not (fortunately!!) who you are. Cheers.