I have used SOAP in many SP solutions so I know how to work with SOAP. I have reviewed the links you've provide, however, I didn't find that they provided any info at all on SOAP, only on REST which NOT what I need.
I have tested the exact soluction I need in my SharePoint site which is hosted on Apps4Rent.com and it worked on first try so there no issue at all that what I am trying to do IS easily doable. However, when I perform the same simple steps in SP online I get "The server returned a nonspecific error...."