Well, first, I would say that actual anger/aggression is not a good idea. Play anger within a scene is one thing, but when you bring the actual emotion into the picture, things can end up very bad. Now, you seem to have thought it through so I will leave it alone.. just.. be careful.

Now, to your question...

I don't have experience with your problem, so I can't offer much advice as to what is safe or not in that respect, but.. there are other things that can be used on areas that are not safe for paddles and the like. Wax and needles are two examples I can think of right now. If you need the pain but cant be beat/flogged/etc in certain areas, that might be a possible substitute.