Regarding Chabad and Moshiach, we all hope for Moshiach every day, as one of the Rambam’s 13 Core Beliefs. The only way Chabad would be ‘vindicated’, so to speak, is if Moshiach turns out to be the Lubavitcher Rebbe. (To quote at least one Gadol, let it be the Lubavitcher Rebbe, as long as he comes already…)
Regarding the use of gematrios to prove a point, see the sefer Degel Machnei Efraim (grandson of the Besh”t) Parshas Chukas, on the possuk Al Kein Yomru Hamoshlim. You can use this link: https://hebrewbooks.org/pdfpager.aspx?req=3723&st=&pgnum=155&hilite=.