Buy lockpicks

Any merchant will buy stolen items from you if you have maxed out your mercantilism skill tree. This requires at minimum, level 18, and is probably not something you should shoot for right off the bat.

If you want to sell your stolen items before that, you'll need to find a fence. There's one at Star Camp.

I think you're asking the wrong question.

Destructibles have two main purposes in KoA.

First, like so many Zelda games before it, it's always worthwhile to run around smashing pots, barrels, and everything else because someone stashed money in them. There's no reason to not take this free money, especially since gold doesn't take up any inventory space.

The second, is that destructibles have a tendency to hide chests and other interactable objects. In this case, the piddling amounts of gold you might glean from the destruction isn't the focus - the phat loots in the chests are. If you're unwilling to hunt down these boxes, you risk missing out on something much better, especially if you've got Detect Hidden (which gives greater chance for gold from destroyed objects)

The problem that you're running into, is that it's tedious to run around and make sure that every crate is smashed. So my solution? Stop running around smashing barrels. If you're investing into Archery, use your bow. It'll auto-target the destructibles and it shoots much faster than you can swing your melee weapons.

I thought the bow was the go-to choice to fight the barrel infestation. And then I found these bad boys.

Chakram's are ranged AoE weapons of awesome. All you have to do is get marginally close to your target, then tap a button and they all break.

Before:

After: Elapsed time: 1 click.

The charged moves are especially useful, and even investing only a single point will net you enough AoE to clear entire rooms (of barrels and enemies) with ease.

And where would I be without an appropriate picture to demonstrate the storied tradition of protagonist-on-crate violence‽