There’s a famous klal in psak- you don’t go after aggadeta. The gemara discussing the idea that moshiach can be from the dead is just as relevant as the gemara saying there is no moshiach anymore. Shkoyach on your abarbenel, but mainstream Judaism rejected that idea years ago. I know it’s much easier to say the Rebbe didn’t die, which is why many are forced to say such nonsense.
But, like Rav Aharon Feldman shlit”a said, those who believe the Rebbe dies and is still moshiach are making a mistake but aren’t apikorsim, unlike the ones who say he’s alive. So a tip of the hat for being within the fold. Kemoscha yirbu beLubavitch.