Saddest,
It is not 'too late' for your ds 13. Try simple boundaries, with stated consequences (like removal of electronics/games-if he ups the ante know where the master electric switch is and throw the whole house off).
Do not yell. No name calling, no comparing him to step-dad. Tell him it is important for him to be able to behave (in a gentleman like way) even when he is mad/angry/sad as well as jubiliant/celebration. Point out stupid behavior you see on the news, just for conversation, "that guy could have handled it differently, no doubt".
Good luck, this does take back-bone and time and don't give up. If you feel you said something out of line and hurtful, then say you are sorry and you need some practice too. At any rate, acknowledge it-people do slip up...show that it can be resolved and then things move on without the tense, stomach knot for hours/days on end.
Forthebestagain,
Well, I'd tell him to do 'it' outside and to try not to make too much of a mess.
Dismissiveness it the only way forward with this circumstance coming from an abusive adult, imho. I would always take a suicidal comment seriously from anyone under 22-24 or so. But from an EAer, it is clearly a manipulation tactic.
Silence is best.
How is your new hobby going?
It is a big leap, a bold stroke for the beauty, health, fresh air for the rest of your life. Courage and focus. What you are doing is valid and clearly the right thing to do.