Rob,
I think you've well covered everything here. My only possible addition comes in the form of a time frame; that is of course if there's going to be any kind of exclusivity - if not, no problem.
It's just when I've done this in the past I've always had a set time frame; ie 5-year exclusive before I could offer the deal to someone else.
I also ALWAYS had a money up from + residuals. If they really want you, they will pay.
Paul