I may be mistaken, but at least on my 2001 I found it interesting that although the pulley had splines the crank end did not; it relies on only the woodruff key and friction. My suspicion as to why, is that perhaps this decreased the metal to metal contact between pulley and crank to ease removal, but of course that’s just a guess.
If the pulley was wobbling or slipping I think I fear the worst. I think that once they start moving about they mangle the woodruff key slot in the Crank. I hope you are lucky and it’s only the pulley and key.
The early Miata with a short nose crank suffered much the same thing and there are some fixes out there, but not really sure how much success they had.
A search for Miata Crankshaft Repair will show their situation.....
miata crankshaft repair - Google Search
Here is an image of my crank end where you can see the marks remaining from the splined pulley.
Good luck with it, please let us know how things go.