I am concerned that you are just "digging the hole deeper" and making your "rearrange and clean up" 100 times harder.
15K of images in a catalog is "Tiny". Lightroom catalogs can handle far more than that. And ONE catalog is always recommended.
You must note that Catalogs are not connected in any way- changes you make in one are not reflected in another. So if you "Export a Catalog" and make changes to the exported catalog, these changes do not happen in the "Original" catalog. Move folders/files in the exported catalog and you have just created missing folders/files in the 'Original" catalog-completely messing it up!!
My advice would be to NOT export extra catalogs. Do ALL your cleanup in the "Original" catalog.
You will find some great advice at-
And (back to your question)- I cannot answer. Are you sure that history exists for the photos in the "Original" catalog?
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I have gone to the front of the catalog (2004ish) and exported a few to a catalog, but when I open it no develop settings.
What does this mean? Exactly where are you looking that you don't see develop settings?
I agree with WobertC, this seems like work that could make something worse, and also, perhaps there are easier ways to get there. But if you're absolutely convinced you need to do this (I am not convinced), make sure you have backups of all photos and your catalog file before you start.