Hi Tevelygo. That is interesting about alexithymia. Mainly, because I'd never heard of it before! I myself have not always been connected to my own thoughts and feelings in the past and therefore didn't identify them correctly. I think that's what a counselor is for though. To help, really, in any way. Therapists have many different personalities, and who knows, maybe you'll find one you will click with more. You said you didn't see how therapy was helping...but a good counselor will help you through your anger with this issue and give you tools to help yourself. I say consider finding another counselor. Maybe even just for short term.

When you say "since then, every time I run into people who abuse my good intentions, this anger increases" do you mean when you run into the people who have hurt you? Or just anybody who happens to take advantage of you?

Regardless, I'm sorry you were hurt and experiencing the after effects of it. I know what it is like to feel anger and other negative emotions around an unresolved issue. I don't really have an answer per se, as to how you can overcome it. I can tell you what I know though and what has helped me, a person who has...not exactly resolved all their issues, but who's heart still beats and who survived people being hurtful and coming out with the "shorter stick," in arguments of oneupmanship.

1.) Write about it. Write about it as if you were going to publish it into a personal essay in a book. Tell your story.
2.) While you are writing your story, ask yourself how you want your story to continue or end. How do you WANT to live your life? Then find ways to do that.
3.) I do not recommend trying to hurt the other people who have been hurtful to you. There are many reasons for this but the reasons I can think of is: a.) it's immature and hypocritical (i.e. "you hurt me, so I hurt you"), b.) it could blow up in your face and you could end up more hurt.
Edit: It does kind of sound like you already did this, by burning bridges. I don't know though. And so I'm editing my comment here. I hope you do not feel judged by my #3. Its not meant to be judgmental. Just advice from what I personally go by.
4.) Write, again. All your negative emotions about it and them, and how they hurt you and behaved and how pissed you are about it. Maybe even write them a letter. Don't send it. Burn it. It's a way of letting go, I have been told, though I've never actually tried this one.
5.) Google is your friend. Google: "How to let go of anger." I think a lot of things come up.
6.) Distractions help. What are some things you enjoy? Do them.
7.) I have found that exercise really helps put me in a better mood. Even just walking, which is what I do a lot of the time. It burns off my negative emotions. It puts me in a better mood.

Best wishes to you.