I think I completely understand and agree with your assessment of what I have been taught to call "The Great Mystery" - all that exists (and doesn't exist) in this realm and all others. I had trouble defining for myself what my beliefs actually were for some time. I did a lot of comparative religion studies in college and none seemed to fit what I felt was Truth. They all had some Truth in them, but nothing seemed to fit completely.
So, I took bits and pieces from all and basically followed my own Spiritual Path. Eventually, I did find others who were a part of a very ancient religion that did fit, and I've been a dedicated follower ever since. This new commitment has helped me to come to terms with what I've believed to be Truth since I was a child by putting a framework around it and giving me words to tie it together.
Some may argue that words that describe spiritual experiences are only labels and labels are inherantly limiting. They would argue - and have - that the experience is what is most important, not what you call it. They may be right, but for me, having the labels has helped me to put my arms around things and help me solidify my beliefs.
I don't know which would be better for you, only you can determine that, but if you think it would help you, I'd be happy to share some of my "labels" with you.
All that being said, I do have some thoughts about your experience and how that changed you.
Sometimes the things we perceive as bad are actually the things that are sent to help us.
Change does not happen readily or easily for most people. We live in Fear. Fear of death, Fear of life, Fear of discomfort... Our whole lives are built around not being uncomfortable. Many times, most times actually, change is uncomfortable. It is also necessary if we are to grow both physically and Spiritually.
I can't say that what you experienced wasn't some form of malignant spiritual entity; it may have been. But I'd like to offer for your consideration the possibility that it was in actuality, an Angel or Spirit Guide giving you the Spiritual equivalent of a swift "Kick in the ass" to get your head right and quit abusing yourself and others.