> I'm no lawyer, but as soon as someone takes off with my stuff, that sounds like theft.

I expect it's not theft. In England the intent requirement is famously "permanently to deprive" and so any situation where you're getting it back isn't theft. Doubtless the US has slightly different rules but I don't think that'll be theft.

In England, can I take someone's belongings and extort them to pay for "shipping and handling" fees or compel them to go out of their way to some risky nondescript location to pick it up? Wonder what the crime in this case if it's "not theft".

The U.S. has very different rules. Just yesterday there was an incident in my town where a couple of guys drove a car out of a parking lot, then later drove it back to the parking lot where they were apprehended and arrested for theft.