So this turned completely into a Mac issue. As mentioned in the above post, Wwise on mac does not create a cache folder. So I used another Mac in the house running Windows via bootcamp and created a WEM file easily with Wwise. Than tried creating the psarc back in OSX on my other mac and ran into nothing but errors in the RocksmithCustomSongToolkit, after repeatedly being bombarded with errors upon trying to generate the psarc - I transferred the files over to the other mac running Windows and installed the toolkit there and it generated the psarc file first try! I gues what I learned is if you want to create Custom Songs on a Mac, Windows running via bootcamp is required. I couldn't get anywhere past EOF in OSX. Thank you again for all the info provided here! you guys are awesome!