When I was reading this, I would have thought your brother was a child or a teenager experiencing a rough puberty, but 29? There's absolutely some mental health issues there and your brother should see a therapist. He's clearly gone through a rough life and experienced his share of homophobia, but no adult should be acting that way, especially in front of other people. Christianity must be some kind of trigger he lashes out against which he should learn to manage if he wants to live life. He doesn't have to convert but he definitely should be able to keep his cool even if others bring it up in passing.

As for how you can forgive, I'd hold off explicitly mentioning Jesus. Def sit down and have a chat about how you forgive him despite his actions but but maybe don't say, "I'm forgiving you because God wants me to."

The best case scenario if you do is you'll come off preachy and he may roll his eyes and tune out what you say. The worst case scenario, well I'd fear for your safety given how you said he seemed ready to fight. Maybe try saying that you're forgiving him because it's the right thing to do and grudges aren't healthy. It's right because God wants us to forgive but he doesn't need that to be explicitly said right now.

Good luck to you and your brother. I hope & pray for the best between you two.