1) Is the front panel audio connection shielded as well as the cable?
Both audio & USB cables are shielded.

2) Is the front panel circuit board grounded? I don't see a grounding wire on it.
Yes, both audio & USB are grounded, when both screws are screwed to the chassis.

3) Is the audio ground also connected to the USB ground on the front panel display circuit board?
Yes, as above