The way I see it. You didn't cheat. You were in transition but weren't with anybody.
His strong reaction does border on abusive. One doesn't have to lay a hand on you to be abusive. Saying he has thoughts about harming you is a gigantic red flag. IMHO
Over a year ago I cheated on my boyfriend. It was ugly and nasty and all associated with my then untreated mental illness. After a six month or so separation. We started to talk again. There were conditions to getting back together. Each of us needed individual therapy, we would go to couples counseling, and we went to a couples IMAGO workshop to help us communicate better. We are engaged with a date set for May 18.
It was possible to fix a flat out infidelity. It also was a lot of hard work on both our parts. It only worked because we took actions to fix the relationship and we both wanted it to work.
Hope that helps.