Is it Arnold? I think Arnold has a feature of stitching those seams automatically even on UDIM patches .Also the geometry shouldn't have splits, hard edges. It's based on my Max experience although, not Maya
Also, you should be exporting a 32bit .exr. That way it's straightforward on the other end, Vray or Arnold or whatever. Your UVs should be packed a lot better(or use UDIMS) The face(most important part of the character) is only using about 10% of UV space. The face should be on its own separate UDIM tile.