Cs, an army of shluchim is not a sign of a Messiah. That army was not “kofeh kol yisroel” to keep the Torah, as the rambanlm stipulates. The vast majority of klal yisroel became less religious during the lifetime of the Lubavitcher rebbe, with conservative growing in America during the 40s until around the 80s. And even when they declined, it wasn’t because they were all becoming frum; the intermarriage rate only increased.
At the time the Lubavitcher rebbe passed away, 90% of world jewry were not frum. Now more are, but it’s due to having more children and intermarriage more than the BT movement, which currently is almost entirely among sefardim… Ashkenazim have an intermarriage rate of more than 70% now .
So did the Lubavitcher rebbe bring all of yisroel to the Torah? Not by any stretch. Not even close. Not even close to being close to being close. Rav saadya gaon brought far more Jews back during this fight against the karaim, and nobody thought he was moshiach.
As for yichus, there were many gedolim who were descendants of dovid hamelech, including all of the rebbes of riszhin.