There isn't an exact word/character limit when using the text editor for creating blog posts. However, there is a hard size limit for the amount of content you can enter into blog posts The page content limit is 64mb. This goes for things like Pages, and Blog posts. So if you are running into issues, I would recommend resizing any of your images to save space.
I hope this helps. If there is anything else I can help you with, please let me know.