The problem here is that when someone does crack this, for sure they'll just cash out your btc if it is larger than your reward.
Pretty sure that's only one of his addresses. He has not revealed any other encrypted private keys except that address's which has only 0.15 BTC in it. So whoever cracks that won't be able to get access to the rest of his wallet.
@OP for the 0.5 BTC reward you should escrow it to increase the legitimacy of your offer, especially as you are a newbie.
How am I supposed to escrow it? I don't have the keys for it! I suppose you could have a middle man receive both the private key from me and the password from the other person and send us our respective amounts - fee. Im happy to do that