To disable Tax calculation, just leave Sales Tax/VAT unchecked in the settings of every product, or go to Seller Admin > Cart Sales Tax & VAT Calculation, uncheck everything in there (and delete anything you may have in the Advanced Tax Settings box), and click Submit.
To disable Shipping calculation, go to Seller Admin > Cart Shipping Settings, select your Country and enter your ZIP code (or just enter 00000 if you're outside the US), make sure everything else on that screen is blank or 0.00, then click Next to proceed to the Shipping Rules screen. Select and Delete any rules you may have in the Existing Shipping Rules menu there, then click Back to Admin.