There is only one thing that stands out for me in your status reports, and that is from top(1): Xorg is in an ACPI lock state. This has been
previously reported to the misc@ mailing list by someone with similar hardware. The discussion
continued on tech@. I did not see a resolution in either thread.
I noted that your swap size and RAM appear to be 1:1, not 2:1, and at 1:1 it is possible that swap is not large enough to store a core dump in the event of a kernel panic or by your forcing one through ddb. Note that kernel core dumps will only be stored on the default swap device, should you have more than one.