for changing the port, set a Environment Variable (System Variable) under System Properties called PORT and point it to any port number you want to use. After starting Studio, you will need to manually address the new port in the browser's URL, as the "Open" button is hardcoded to port 3000 - so e.g. to http://localhost:<newPort>
Same manual port change goes for the Preview tab, as it opens with port 3000 as well.
R&D also already created an enhancement for this to get it configurable more easily and more integrated in a future version of ThingWorx Studio.
I hope that helps...