If it's not a late-model car, they can probably do this, as long as the repairs meet automobile repair industry standards (there are such rules published, although I couldn't tell you where to find them).  If you were a lot closer to 100%, you might be able to persuade them to total it by being difficult, but that's not going to get you anywhere with this big a difference.

No car, it seems, ever is the same after collision damage is repaired.  But the law doesn't take that into account, and you, like everyone else who's been through this, are just going to have to live with it.