Spoilers
I also got ending 12 at first, and while I did feel the exact same sequence of emotions you did (disbelief and irritation at everything supposedly being a simulation, excitement at the book thing, gladness that there was a way out mixed with a feeling of that particular element being a bit rushed), I still decided it was my favorite ending emotion-wise at the end. We made all the right choices and saved everyone we could, got true closure with Ash, and unlike all the other endings, the future is left open. I would've appreciated more - maybe a weird boss fight with some sort of personification-of-data-corruption entity, or something similar to spice up the journey through the glowing door, or maybe finding our missing wedding ring at some point - but I still like it nevertheless. I hope you also enjoy the various other endings as I did.