Nutra, quick thing - I'm deaf, and my best friend in high school was also deaf. We did talk while driving, but only because a) I can sign one-handed, and b) I have excellent peripheral vision plus I do mirror checks so my eyes did occasionally slide over to the passenger side (to check the mirror) more frequently. It was slightly awkward for us but we could still converse reasonably, although my friend did keep an eye on the road just in case. She never had to warn me to brake or anything like that. Dangerous? Yes, which was why we tried to limit such conversation to important topics that couldn't wait until we got to where we were going. So it's perhaps not quite as bad as you think... But then we were reasonable, skilled signers... Anything beyond that gets shaky and I agree, scary to watch.
Just saying that no, you do not strictly have to be facing the person you are speaking to, nor do you have to use both hands.