Menachem shmei, no, none of the meforshim say that Yaacov alive in his kever. A body to be alive needs air, it needs food, it needs water, it needs to do bodily functions.
If there are more people in Chabad who believe what you believe that is absolutely insane. Your belief is like the anceint Egyptians who embalmed and buried their Pharoahs and also buried them with chariots, wax dolls in the shape of women, weapons, etc. because they believed their bodies only partially expired and will soon start living again in the afterlife….shame on you to believe such things.
You are using Torah sources and twisting them to further your a”z ideology just like the Tzedoikim, the Keruim, the Christians, Shabsi Tzvi, and others did to try to “prove” that their ideologies are the truth. At the end of the day Chabad a”z will also lay in the dustbin of history while the truth marches on. But until then, it will pull down with it into shaul tachtis many, many Jewish neshumos H”y.
You cannot argue with posukim in the Torah, period. No mefoiresh does that. The posek says clearly, Yaacov expired, Yaacov was embalmed, Yaacov was buried. End of story. It also says Yaacov did not die and not dying can mean many things. To further your a”z ideology, you claim Yaacov is alive in his kever. That would be a huge tzaar on Yaacov. Would you want your body to be alive in your kever for thousands of years not being able to move? Not even the murdererous Hamas has people in their kever alive for thousands of years. It’s absolutely insane that you would think that Rashi and the meforshim claim that this is happening to Yaacov.
To believe in a”z you need to be slightly insane to believe in the narishkeiten attached to such beliefs.