All particle physics experiments depend on Lorentz transformations which describe perfectly electric and magnetic fields and how they transform with changes in velocity.
No false results have been detected and so Lorenz transformation calculation are trusted to give changes due to to velocity, see page [three here][1]. 

>Is there any difference between ether and EM field?

The luminiferous aether as hypothesized before the Michelson-Morley experiment was discarded as a concept because it was not Lorentz [covariant][2], as was necessary for the Maxwell equations to work correctly. Up to now Maxwell equations are continually validated.


  [1]: https://www2.ph.ed.ac.uk/~playfer/EMlect18.pdf
  [2]: https://en.wikipedia.org/wiki/Lorentz_covariance