why did Driver had to show the jew mobster where the money is?

"Irene, look. I know you're upset with me now, but you're loser husband brought this on himself. I tried to help him, but he was too big a nitwit to save his life. Now, you and your kid are in danger because of his stupidity, and I am the only one left to protect you. On top of that, I have 1 million dollars in cash that can help us start a new life, and you decide if you want to do it with me or not, but right now we gotta get out of here, let's go get the boy at school. Some bad people might be on their way here to hurt us so, let's use the stairs."

THAT, while still impractical and risky, is the best way to protect Irene and the kid while avoiding confrontation with the mobsters. With a whole mil they could have bought their way to Mexico a few times over. Now, instead, unless Rose's mob was actually comprised of just 3 people, someone else will rise up in rank and most likely go after him by using Irene and the kid as bait. Which is ok by me, because it could be a nice idea for a sequel.