Which input volume bar did you set to maximum? Assuming you are choosing pulse or default in Audacity’s Device Toolbar the Audacity input slider should be greyed out on maximum (that is, it has no effect).
Pulse is often problematic although it makes it easier for multiple applications to use the sound card. If you want to use pulse I suggest you install Pulse Audio Volume Control then choose the input source and adjust the input level using that. Then to launch Audacity, open a terminal, type:
env PULSE_LATENCY_MSEC=30 audacity
and hit ENTER on your keyboard. This should solve the crackling, fast playback and freezes.
Otherwise, choose the (hw) playback and recording devices in Device Toolbar. However because you are now trying to access the sound device directly through ALSA, if any other program is accessing the device then it will not be available for Audacity. Also this denies exclusive access of a device to PulseAudio, so other programs using PulseAudio will not be able to use that device.
Gale