How do I return this useless piece of rubbish?

As far as configuring, you can use the zwave tweaker. You just temporarily assign any zwave device to the tweaker device type handler, configure it the way you want, and then assign it back to the everyday device type handler.

With regard to the other issues, if you’re not happy with SmartThings then don’t keep it. Every system has pluses and minuses. SmartThings is flexible and powerful, but as you’ve discovered, it’s not always easy to find all the features. And it’s primarily a cloud-based system, so it just isn’t going to be quite as quick as a fully local system. If that doesn’t work for you, there are a number of other alternatives. You might find the following of interest: