Everytime we export stills from FCP5 HD from our HVX200 shoot we only get 72dpi resolution even though we supposedly got 960x720 from our 720p/24PN capture. Surely that's not the best we can do! I thought ending up with only 960x720 in the footage was bad, but I can't make a poster out of 72dpi. Yikes. Anybody know how we can get the highest resolution from the export?

The pixel resolution from the HVX is 960x720. That's it. there's no way around it. That 960 horizontal figure is stretched to 1280 upon playback.

It seems that you might be a little fundamentally confused about what DPI means...it's a figure to connect printing sizes to real pixel dimensions. But the pixel dimensions in this case are not adjustable or variable.

FCP will always export HVX footage as stills as 1280x720. There is no better.

The HVX only captures so much resolution... if you want a high DPI, just print into a smaller area. The frame can be 150dpi (or higher) if you want... it'll just print onto a smaller area.

In Photoshop, you can fake a little extra resolution by:
Resizing in 10% steps. i.e. 110%, 110%, 110%, ...
instead of doing ~130% in one shot

And then apply a little unsharp mask.

Other than that, that's about all the (apparent/fake) resolution you're going to get. It's not going to print well more than a few to several inches. If you need more, use a digital or 35mm still camera.

2- If you can draw / have some artistic intuition, you can sketch the image and make it stylized. Use the video frame as a reference.

Yes, 72dpi is the standard screen resolution for digital photography. As the previous posts have explained, high resolution is a function of how you tell the printer to print. IE, a 1200x900 picture will be a low res print at 72dpi of 16.66"x12.5" and a hi res print at 300dpi of 4"x3".