How much changes can you make to a paper between acceptance and camera ready? [D]

We have a paper accepted to NeurIPS, but at the same time we were working on a resubmission to ICLR just in case NeurIPS rejected us. There has been substantial rewriting, and we feel it would be a waste if we discarded all of it. To give a summary of what's changed: We completely rewrote every single section except for the results and conclusion. We even changed the paper structure. Intro, related work, and background knowledge were completely rewritten to avoid confusion. Method now has a pipeline graph, and all the text detailing each block in the graph. Previously, it was dumping formulas, so the entire section has been rewritten. We also added some scaling and smoothing to our algorithm so our method is more stable. But this changed a lot of our hyperparameters and the sensitivity study's graph. (The entire shape of the graph changed) We added 1 new theorem with 5-page proofs in the appendix. This came from one of the attacks by a reviewer, we answered the attacks by proposing 1 new proposition during the rebuttal. But when we formally wrote it down, it turned into a full theorem with a 9-page proof. This would have changed our entire theoretical contribution. We really don't want to discard it, but not sure if we can add something this big in the camera-ready. Remove 1 word from the title. Change our theoretical contribution, but the method and empirical contribution remain the same. Added about another 5 extra pages in the appendix explaining experiments and metrics (reviewers asked for them). So 14 extra pages in total. Does anyone know how much change for camera-ready is acceptable? Can a paper get rejected if we change too much during camera ready or they will just tell us this is not acceptable please re-submit something closer to the version during review?