I think you can push a little against the magnetic field to rotate and change your orientation, but to gain height the magnetic field is not useful.
[Edit: Mmmm I'd change "but to gain height the magnetic field is not useful." to "but to gain height pushing against the magnetic field is not efficient."]
If it can accelerate forever, thats proof enough for everyone. However violating the conservation of momentum is a Big Deal. Mathematically that shouldn't be possible due to Noether's. The bar to proof is therefore very high.
With enough proof you can convince the physics community, even if the result is initially weird. My favorite examples are https://en.wikipedia.org/wiki/Wu_experiment and https://en.wikipedia.org/wiki/High-temperature_superconducti... .
I think you can push a little against the magnetic field to rotate and change your orientation, but to gain height the magnetic field is not useful.
[Edit: Mmmm I'd change "but to gain height the magnetic field is not useful." to "but to gain height pushing against the magnetic field is not efficient."]