Speaking as someone who has come through a similar trauma, I have experienced problems very much like yours. It has taken me some time of following this thread to be able to post a response but I felt like I really needed to do so because I have been there and maybe my experience can help.
The Freezing up. Yeah been there. Still happens sometimes but not as much as it used to. Freeze response is part of the fight/flight instinct. Doing a little research on this will help you to understand better what is happening. When you understand what is happening it gets easier to work through it.
Rest assured that this is normal and it can be overcome. I make part of my living dealing with overcoming fight/flight responses in large prey animals. Desensitization is the key here.
Avoiding the thing that makes you lock up will never help. You are right about that. You need to put yourself into those situations a lot and work through them. The thing about fear is you can't keep running away from it. If you know logically that there is nothing to be afraid of then you can stand up to it and work within it until you get past it. It is uncomfortable unpleasant and very very hard. But you/we have survived worse... right?
In order to do that you need to have the help of your teacher. Telling him/her a bit about your past and explaining what your problems are can be extremely helpful. I also reached a roadblock in my training about two years in because of these issues. At this point I knew my teachers well enough and trusted them enough to tell them (in writing, because I still really could not talk about it) about my past life. It wasn't easy at all but it really helped. It helped them to know how to help me and just sharing the burden with somebody whom I could trust was a tremendous relief.
It is also very useful to talk to someone. If not a professional at least someone that you can trust with your darkest secrets and who is willing to listen with understanding. You don't need pity. You just need someone to hear you and to say that what happened to you is not okay, it is not your fault and that does not mean that you can never be strong or happy again.
Don't avoid what scares you. Look it straight in the teeth and tell it that it can no longer control you. With a little help. You can do this.