Ps3 – How to make PS3 recognize an HDMI to VGA converted cable as a displayable screen

According to the online user guide, there is an apparent way to circumvent the PS3's shutdown:

Even when [On] is selected, this feature (HDMI Control) may not be available in the following cases:

• When using certain features of the PS3™ system, such as gameplay or video playback.
• When the PS3™ system is not selected as the input source for the TV.

So it would seem that changing the TV's input before shutting it down should leave your Playstation running.

My TV (Samsung) has specially marked HDMI ports. There are 3 total, but one is marked PC. This port does not overscan, if the 'category' is also set to PC.

It sounds like your PS3 is broadcasting an exact resolution image, then the tv is trying to compensate for the overscan. See if the HDMI Ports are labeled as such, and potentially name the port (in your TV menus) PC or Game (although it sounds like PC would be preferred in your case).

With all of that said, a friend has an older widescreen TV and is unable to disable overscan on it. He had to settle for changing it in his PC. The bad news is it doesn't look like you can adjust overscan in the PS3 as a global setting at the moment.