Hi,
Welcome to TSF!!
Thank you for all the information this is all very helpful, most people don't give us this much to work with!!
Lets see if we can get you going. I would like to know three things to get you started. I would like to know what is the brand and model of your external mic, and what soundcard you have in your computer. Last I would like you to copy this command into terminal.
Code:
lspci <-- l is a lower case L
Lets start with that and see what we get then we can move on from there. I have great confidence that we can get you up and running.
Cheers!