Be aware that even though you loose the window so you can see yourself, the audience can see both your PowerPoint and your webcam.
Here is how you as the presenter can see both.
With the PowerPoint file open, go to Set Up Show and then in the Set Up Show window, select the Show type: "Browsed by an individual (window)" and click OK. This setting can be saved with that PowerPoint file so it opens that way everytime.
This puts the PowerPoint show in a resizable window rather than full screen. You can then have your webcam in a seperate wndow and look at them both. Drag them around the screen until you are satisfied.
NOTE: During the broadcast, if you click on anything except the PowerPoint window, you have lost control over your PowerPoint slides. If this happens, just click in the PowerPoint window to bring it to the front, and now the keyboard and mouse can operate the slide advance.
Only one program on your computer can use the keyboard and mouse at one time. It is whichever you click on last.