As an aside, it would be best to post your own Post as a stand-alone post. By attaching it to someone else's post, your post looks like a follow-up; not an 'original post'. See what I mean? So beings 'we' are so late in seeing your post (which I happen to 'stumble' on), I'm e-mailing you to notify you.
You didn't make mention of using a Paper Tiger. Vinyl wallpaper, unlike paper-based wallpaper, WON'T absorbe any of the solutions you tried in order to break down the glue. The Paper Tiger is used to perforate the vinyl so the solution can get 'behind' the wallpaper and 'attack' the glue.