RE: How Do I Generate A Set-Difference With Context -

It's bad tactics to suggest that you're 80% of the way to a solution, and
not show us the 80%. No-one wants to redo the work you've already done on
the off-chance that they'll be able to help you with the final 20%.

That's especially true as it's a difficult problem and one has to do a lot
of guesswork about the requirements. What output would you expect if the two
source documents are:
<snip>
Sorry, but suggesting improvements to code I haven't seen is beyond my
abilities.