1) I saw a vort in the Ohev Yisrael this week that I was about to post and then I found I had posted it already back in 2012. I hate recycling, but it's worth repeating. The Ohev Yisrael comments on the pasuk: וַיִּשְׁלַ֣ח מֹשֶׁ֔ה לִקְרֹ֛א לְדָתָ֥ן וְלַאֲבִירָ֖ם בְּנֵ֣י אֱלִיאָ֑ב וַיֹּאמְר֖וּ לֹ֥א נַעֲלֶֽה׃ Everybody knew Dasan and Aviram were troublemakers. They had a history. There are certain kids that the teacher has heard about even before he/she walks into the classroom and the second trouble starts, he/she knows where to look for the root cause. Moshe tried to undo that. Moshe said, "From now on Dasan and Aviram should be called by everyone 'Bnei Eliav.'" How we refer to people shapes their identity. Call a kid troublemaker, a no-good-nik, and k'shmo kein hu, that's exactly what he will be. Call them 'Dasan and Aviram the troublemakers' and that's who they will be and remain. Call them Bnei Ploni the Tzadik and you've given them a different identity to live up to.
This may also explain רַב־לָכֶ֖ם בְּנֵ֥י לֵוִֽי. Moshe was saying, "You are bnei Levi - you are the descendants of great people; this rebellion is not who you are."
Unfortunately, Dasan and Aviram chose to respond, "lo naaleh," and reject Moshe's advances.
In light of the Ohev Yisrael's vort, perhaps the way to read their response is, "Lo," we don't want to just be 'Bnei Eliav' and follow in our father footsteps. Rather, "Naaleh," we will be even greater than our father. We know better and can do better. Lots of children think that if they just do the opposite of their parents they will accomplish so much more than their parents did, they will be more successful, they will not fall into the same pitfalls. Eventually they figure out that the path they choose has its own pitfalls.
Even though we know Dasan and Aviram were troublemakers, it seems that they might have sat this one out. Rashi comments ודתן ואבירםג – בשביל שהיה שבט ראובן שרוי בחנייתן תימנה, שכן לקהת ובניו החנים תימנה, נשתתפו עם קרח במחלוקתו, אוי לרשע אוי לשכנו. If not for oy la'rasha v'oy l'shecheinu, if not for Dasan and Aviram living in close proximity to Korach and thereby falling under his influence, they might not have participated in this rebellion As bad as Dasan and Aviram were, Korach was a step too far even for them.
The Sifsei Chachamim quotes that the Maharashal had a kabbalah from his father that this statement of Rashi is a continuation of Rashi's previous comment: בן יצהר בן קהת בן לוי – ביעקב בקש רחמים על עצמו שלא יזכיר שמו על מחלוקתן, שנאמר: בקהלם אל תחד כבודי Rashi explains that Korach's yichus goes back to Levi but not to Yaakov because Yaakov, in his final message to Levi, davened that his name should not be mentioned in the context of Korach's machlokes (we've discussed this in the past we well, see Maharal). This is well and good in so far as why the pasuk gives Korach's yichus only back to Levi and not back to Yaakov, but why does the pasuk give the yichus of Dasan and Aviram only back to Reuvain and omit Yaakov's name there? בקהלם אל תחד כבודי was not said about Reuvain? Answers Rashi (according to the Maharashal's reading), אוי לרשע אוי לשכנו .
R' Chaim Elazari points out the chiddush implicit in this Maharashal. אוי לרשע אוי לשכנו is not just a warning to avoid negative influences as they MIGHT have a detrimental effect. Were that the case, then Yaakov's tefilah would have applied to Levi alone and Dasan and Aviram and the bnei Reuvain getting involved was their own bad choice. Yaakov's tefilos applied to sheivet Reuvain as well as Levi because negtive influences INEVITABLY lead to harm. It's like a psik reisha, not a davar she'aino miskavein. When Yaakov davened not to have his name mentioned in connection with Levi/Korach's machlokes, Reuvain was implicitely included because there was no chance of Reuvain not being involved given his proximity to what was going on.
2) The Kozhiglover quotes from Mishnas Chassidim that ketores is a segulah for teshuvah. He explains that this is why the greatest offering of ketores done during the year was the offering of ketores in the kodesh kodashim on Yom Kippur, as Yom Kippur is the day designated for teshuvah. All the offerings the entire rest of the year are just a preparation to be able to offer ketores properly on that day. This is why, says the Kozhiglover, Moshe suggested to Korach to bring ketores as a test. Moshe was hoping that the segulah of ketores would influence Korach and he would do teshuvah and regret the whole machlokes.
I would add that when Moshe said to Korach that tomorrow they will offer ketores, meaning tomorrow will be like Yom Kippur, it implies that right now, the day before the big test, is like erev Yom Kippur. There is a din before Yom Kippur of piyus, of asking people for mechila, of mending wrongs. Maybe Moshe was alluding to this as well, offering Korach a final chance at reconciliation.
Today erev Shabbos is Rosh Chodesh Tamuz, roshei teivos זמני תשׂובה ממשׁמשׁין ובּאין. Yom Kippur is right around the corner!