As you have noticed, late hops and whirlpool hops can add a ton of IBUs.
AND, as you can see, this forum is totally dead, it's very unlikely you will get much help here. Try Homebrewtalk forum instead, a lot more traffic there. Reddit is okay but generally less stellar quality feedback. No other forums really have good traffic anymore.
And finally... as luck would have it, I have developed equations to estimate IBUs from both boil hop and whirlpool hop additions. It's all here, two different methods, actually, see top of page, then square-root based approximation equations at the bottom of the page. Hope this helps you or somebody out there.
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