Ellabankss , I been using kindle since it first came out years ago personally I have never had any problems . They have great customer service and have never deleted or gave me any problems over my books or cloud drive. I tend to get my books directly from the publisher or the publishers store sine you get deals.. I wouldn't worry they know people get books from other stores
mishomosh43, to turn wifi off of the kindle paperwhite, you tap the three-line corner area->settings->airplane mode and turn it on. If you haven't updated the firmware, you're now able to turn it on/off while in an e-book.
I haven't had problems with this, but I never keep anything that I haven't gotten from Amazon on cloud . . . I only have the wifi on if I want to sometimes browse or dl an ebook from Amazon, but other than that I keep the wifi off (to save battery).