Same for me I was on hold for +30 minutes

As far as I'm aware you're not allowed to use your iPad at all the take the exam. I don't think ProctorU is compatible. So, no.

If you mouth the words it shouldn't be a big issue. You can cover your mouth with your hand or something. But yes, they do have grounds to tell you to be quiet. My first flex, I spoke to myself and had no issues (it was quite audible), but also my proctor was super nice. It's up to you, but try not to..?