In the debug information, the response back from paypal is:
error: Security header is not valid
The Security header is not valid error message means that the API Details you entered are not correct, they are either Sand box API credentials and you are using the live server, or vice versa.
to turn off debug mode, go to the power store admin settings tab.
For the shipping issue, when adding products, make sure you are entering a weight. Shipping is based on the weight of the cart, so if you do not have a weight for the products, it will not calculate the shipping