Also you need negative mass, which doesn't exist even theoretically, oh and more mass energy than the entire universe
Are you thinking of a wormhole, not a warp drive? I'm not talking about a Star Trek FTL drive, but instead a device that warps space, just like gravity does, but asymmetrically. I don't believe it's possible either, but it's still allowed by accepted physics, and it wouldn't require lots of mass.
I don't think we'll know enough about this concept, or about negative mass, to rule them out until we finally understand how mass is quantized, or, rather, where rest mass comes from in the first place. Maybe when quantum gravity is finally understood there will finally be an explanation for rest mass, but maybe it's even further down the road.
Heck, we can't even measure the rest masses of quarks accurately -- not even one significant digit in some cases -- let along explain the values There's lots of physics left to be done there.
Just because i write down math does not make it a valid prediction.
The math of modern physics has been shockingly predictive. All sorts of crazy shit has turned out to be true - so much so that people believed in String Theory for 20 years with no evidence whatsoever (and some still cling to that belief). Those people aren't stupid: "following the math" has a really good track record. It's best to keep an open mind until we get better theories.