When Google first ranks your web page, no, it won't make a difference (Google is just a robot, so it can't determine what is "readable")

However, Google does keep track of how long a visitor stays on your page, whether or not they found the information they were looking for on your page, etc.

If a visitor can't read your web page, and they quickly press the "back button" to find a different web page to read, then Google will slowly drop your rankings over time, because Google will realize that your web page is not the most helpful article for web searchers.

Yes, very much so. An example is article spinning, all the words are there but if they are out of order, incoherent, and have small problems then Google will have a negative outlook on the content. This causes low rankings in the Google SERPs