I mentioned Jonah's 'Asian honor' remark the other day as sticking out for me as well. Of course, we don't know exactly when he said it or the context. Was it the first thing out of his mouth? It would seem to be close to the first thing, since if we're to believe Dina, he said it to her upon learning of RZ's death and sharing the news with her.
"Extremely early acceptance of suicide" is one way to look at it. Imo, the quickness of this particular response indicates no surprise, no shock, no horror, no 'I need some time to digest this.' Jumping right to 'Asian honor' and the self-stabbing gesture suggests, imo, earlier knowledge of Rebecca's impending "suicide."
Another thought I just had ~ if JS was concerned about the potential for RZ to kill herself over Max's accident due to her "true Asian background," one would think he might have asked his brother or someone else to stay in the main house with Rebecca while he was at Max's bedside and presumably sleeping nearby at the Ronald McDonald House.