Can't import mesh help me pls!

Recalculate won't affect whether or not your mesh imports into Studio. Recalculate just flips faces so they're not inside out. It doesn't always do a good job so if you press N and under shading put a checkmark next to backface culling you'll be able to see which faces have flipped normals. If you need to flip normals select the faces to be flipped, press W > Flip Normals.

This may not be the best way to do this, okay? mauvemorn is the go-to goddess of this stuff so anything she recommends is best. But I would delete everything in your scene except your mesh and clean up the mesh. Select and delete the hands and forearms and delete all geometry that's inside the mesh. Those faces won't be seen and all they do is add to the polycount which, incidentally, is way too high. It's horribly high, actually. You can use the decimate modifier but it will kill your topology and turn it into a mesh. The best thing is to go through and select edges and press X > dissolve edges to lower the polycount while preserving the topology. It's tedious so put on some good music and prepare to work.

Before dissolving edges it helps to turn your tris into quads; it means less edges to get in your way. In the UV editor enable Keep UV and Edit Mode Mesh Selection in Sync. Now your UV islands can be manipulated without having to select anything on your mesh. Start selecting islands then, in the 3D window, press Alt + J. Watch what's happening in the UV editor because sometimes this method screws up the UV islands. If that happens, select fewer islands. One island at a time if necessary. Alt + H to unhide everything. After everything has been turned to quads you can start dissolving edges.

Delete the eyeballs because why keep them? I've no idea what to do with the hair, unfortunately.

Remove all modifiers. Delete all weights currently assigned. The goal is to have a mesh that is clean with nothing assigned, not vertex paint, weights, or anything.

Take a look at this thread here. Hopefully, it'll help. Probably you'll want to join all of the rig's body parts to transfer weights from. Go through that thread for more info.

At this point, your mesh is nowhere near ready to import into Studio.