Personally I think it's great you live in an area where self help groups are available through out the week. I wish there were some in my area. What does long-term therapy involve?

I have no idea about the route cause or symbolism behind the thoughts you described. but luckily there are a lot of ways to extinguish anger with meditation for example. I haven't even discovered the origin or source behind my intrusive thoughts either. maybe you don't need to find out why the anger is there, but find a way how to dismiss it out of your mind. I was taught to first identify it as OCD and basically second distract myself with something else. Over time it gets better just continue to utilize your ability to use logic and reason and it'll minimize the severity over time. Good luck