Menachem Shmei, Rashi himself points to the word in the posuk ” ויגוע” that he expired, he never challenges that. This is what Rashi says: ויגוע ויאסף. וּמִיתָה לֹא נֶאֶמְרָה בוֹ, וְאָ”רַ יַעֲקֹב אָבִינוּ לֹא מֵת . Rashi never said that he did not expire and that Yaacov Avinu was PHYSICALLY alive after he expired. Rashi mentioning that the Torah does not say מות, does not mean that Rashi meant that Yaacov’s body did not expire. We have numerous meforshim explaining what Rashi meant and none of them, perhaps with the exception of “meforshim shel Chabad “, none of these meforshim claim that Yaacov Avinu’s body did not expire.
The “source you mention to prove your point”, Taanis 5B, you leave out the part where R’ Yitzchok, who is the one bringing up that Yaacov Avinu did not die, expands on that that Yaacov will be saved as his seed is alive and will be saved (from captivity). The classic understanding of this gemerah is that Yaacov Avinu is alive through his descendants. Never does the gemorah say that Yaacov Avinu is alive physically.
This is the power of avodah zora, to spin and misinterpret things so that supposedly there is “proof from the sources” in the validity of your worship of your idol.