So good to hear that you've come through the burnout and used it as an opportunity to learn and grow. That is the true purpose of hard times, as stepping stones. And although the experience was painful in the moment, now you can look back and see how it changed you to reach a better stage of yourself. Seeing that change is always encouraging!
Just curious, have you ever taken any personality type tests or done any research on personality theory? What you said about being highly sensitive and empathetic is something I can relate to as well, but I really want to understand where you're coming from instead of making assumptions. My pet theory is the Myers-Briggs Type Index (MBTI), and it includes two different kinds of empathy: receiving others' emotions clearly like a radio signal and experiencing them as if they were your own, or deciphering others' emotions like reading subtext into a story and experiencing them by putting yourself in the other person's shoes. The first kind is called Extroverted Feeling (Fe), and the second is Introverted Feeling (Fi). MBTI types who have either Fe or Fi as a first or second preferred thought process (aka cognitive function) usually exhibit the strong levels of empathy you describe, but I don't know you well enough to guess which one you have or your personality type. If you figure out your personality type, it can make a big difference in understanding why you experience the world the way you do and why some people give you more grief than others.
Anyway, excuse the long tangent, but I'm a personality theory geek, and understanding the way I and the people around me think has salvaged so many relationships that I wish everyone would take the time to study it and make life easier all around. As a highly sensitive person and from the work situations you describe, you seem like a peaceful, conflict-hating person, which makes situations when others are making things difficult for you even more unpleasant. Why can't everyone just show common decency towards each other?