How to adjust the volume with faderport

Audition doesn't determine the record levels of incoming signals at all, I''m afraid - this is determined entirely outside of Audition, usually by a separate gain control on whatever preamp you're using - or in the Windows Sound app. There's no way that your faderport can get anywhere near this - it can only alter things within Audition, and Audition records directly what it's sent without altering it at all.