If you're going to do quickies, then yes, be a clock watcher. You have to. Once they get to the hour range, now you're making enough money to stop worrying so much about an extra 5-10 minutes or so, but if he's going to be cheap with his money, be equally cheap with your time. Give him exactly his time, but no more.... if he already knows he needs more time, why did he book a short session?! That's disrespectful to you.
Don't ever ever tell a first time client that it is okay to be rough. No, it isn't. You don't know him, you don't know his definition of rough, you don't know if he will listen to your gentle guidance. If he wants someone to be a little rough with, he needs to invest in seeing her a few times to make sure they click and have good communication and comfort levels. Your answer when they ask if they can be rough is always "that's only something I entertain with return clients with whom I am very comfortable."
Get wasp spray or bear mace. Keep it everywhere. It shoots 15-20 feet, has a good spread, and hurts a LOT. Bear mace you can get at sporting goods stores. Wasp spray you can get pretty much anywhere. Both are preferable to pepper spray, in my opinion. If the guy has ever been in the military or police force, he might be prepared to handle pepper spray and still hurt you. No one is ready for bear mace.
Hope it gets better for you, hun.