Question Fixing an imported model's rotation ?

Hello. I come here in a time of need as this little problem is driving me insane.
For a side project, I ripped and imported a player model from my copy of Sonic Generations to experiment around creating a platformer with that kind of Sonic feel.

Little problem, the model got exported with a -90° rotation on the x axis, so I just applied a rotation of +90° on the mesh and continued on my merry way.
However, currently in the project i'm using lookAt on the model to make the player model look at the direction they're moving towards, but this applies a rotation of 0 on the mesh, canceling my fix and making a mess.

I then tried fixing the model's rotation on Blender and exporting it to Unity, but for some reason this completely disables any animation I then try to apply on the model. There doesn't seem to be a way to fix this in the FBX import settings, as they're grayed out.

Any idea on how to possibly fix this, in a way that doesn't come back to bite me later on how it did for lookAt ?
Thanks in advance !