Yes. While it works great for regular RAW images, it doesn’t do so well on RAW film scans. You might see that I’ve corrected my procedure in the next comment.
Yes, and there’s also an assumption that the green in your found photo is accurate. 
It looks pretty close to me. I’ve also since made a few adjustments that I didn’t post here. Specifically, I cooled town the overall WB significantly. Thanks for the rest of your commentary, I’m pretty happy with the workflow that I’ve acquired in this process.