We appear to be addressing two different issues.
The OP is trying to get a correct exposure, while others are talking color correction in post.
I think we might be confusing the OP's question of how to get a correct exposure so that extreme measures are not required in a attempt to save a image.
I believe I addressed all that in my first post, the first response on the thread: the histogram shows the whole image, not just the metered part; using a gray card can be tricky due to gloss but works with practice and experience; and a hand-held meter is much superior to a gray card.
But in the ensuing discussion, I've also made note that I use my ICC-based workflow first to determine the proper exposure and then to correct color. Make no mistrake: the first (and, I'd suggest, by far the most important) part of my ICC-based workflow is determining proper exposure settings on the camera and then the proper exposure adjustment settings in development -- and that's precisely the topic under discussion (even if what I do is a bit overboard for what Simon is trying to accomplish).