My .docx can't be previewed when using my iPad or iPhone.Is it too long, and why is this happening?

I did a lot of tests losing a lot of hours. First of all, if I try to access online I get the error: .docx files are supported, but an error occurred. Having said that, I tried deleting 1 chapter at a time to see if the preview changed and therefore the file fixed itself. I delete several chapters and when I delete chapter 43, as soon as I try to save, suddenly the file opens on both the iPad and the iPhone. Without the chapter in question, we are on page 1429 and so far everything is ok. Without adding the chapter, to understand if it was a page-related problem, I started adding about 20 blank pages and the file still opens. I tried again to add one page of the chapter at a time and after adding only one page, the problem recurred, so I came to the conclusion that the problem is due to the number of words and probably not to the pages of the file. In my case, they manage to open correctly, file with approximately 502594 words, i.e. 1429 pages, 39403 paragraphs and 79680 lines. I still wonder what the point is if the official website lists 160 MB as the maximum limit for doc files, if it then cannot manage a 30 MB file , where you simply need to reach a word limit to no longer display the file correctly. This is a huge limitation because to view the file normally, I would have to convert it to PDF and then open it. This means that for every change I make to the Word file, I would have to remember to delete the old PDF and convert the Word file into a PDF file every single time for every single change, I find it really absurd and above all limited. I have given you all the information possible to investigate the problem and I hope you find a solution as soon as possible.