After reviewing your pastebins and consulting with the folks in #pulseaudio here is what we will do. Open a terminal and type pactl list sources to verify that the Line In is the active port.

Source #1

    State: SUSPENDED

    Name: alsa_input.pci-0000_00_07.0.analog-stereo

    Description: Built-in Audio Analog Stereo



--SNIP--



    Ports:

        analog-input-microphone-front: Front Microphone (priority: 8500, not available)

        analog-input-microphone-rear: Rear Microphone (priority: 8200, not available)

        analog-input-linein: Line In (priority: 8100, available)

    Active Port: analog-input-linein

    Formats:

        pcm

Once that is verified, we are going to check to make sure we are able to set the port with the pacmd command. pacmd "set-source-port 1 analog-input-microphone-front"
Run pactl list sources again to verify that the Front Panel is now active.

Source #1

    State: SUSPENDED

    Name: alsa_input.pci-0000_00_07.0.analog-stereo



--SNIP--



    Ports:

        analog-input-microphone-front: Front Microphone (priority: 8500, not available)

        analog-input-microphone-rear: Rear Microphone (priority: 8200, not available)

        analog-input-linein: Line In (priority: 8100, available)

    Active Port: analog-input-microphone-front

    Formats:

        pcm

If all was successful we can now put that at the end of your /etc/pulse/default.pa file as such:

set-source-port 1 analog-input-microphone-front

As a matter of interest though, you should be aware that PulseAudio is supposed to manage this for you. It should be switching to the Front Panel mic when it is inserted automatically (provided the hardware supports device detection).