It seems to me that you had bursts of violence because you felt hurt yourself and needed to make things 'right', not just because you found joy in harming others.
I also have a really low resting heart rate, around 40 beats per minute.
What you didn't mention in your original post was that you'd done most of those things out of retaliation - not premeditated. That's a major difference from being a psychopath.
However, I think my situation is much less severe - I've never caused anyone any more than bruises (nor had blackouts), I would certainly say that the anger I have is a mental health issue. Not at a criminal level, but certainly at a level that can cause problems with work/life relationships.
I've went to see a therapist for about a year and it's really unbelievably helpful.
I wish going to see a psychotherapist was as easy for people to do as going to see a physiotherapist.
I've never seen a therapist, and don't know what anger does to you, but for me it's not a mental health issue.
Part of it I'm sure is that I don't bottle anything up any more, and the other is that I'm not a kid and being picked on is just laughable. I think knowing that it's okay to be angry, that it is a normal thing that is perfectly okay, was probably the biggest revelation.
The people you spend most of your time with and your therapist might have a different opinion of you than yourself.