I'm guessing that the damaged wheel has gone egg shaped to split like that, a trait of linked to low profile tyres, hard suspension settings, and repeatedly driving over speed bumps, and potholes, although that wheel could easily have the crack welded successfully, its likely to crack at the next weakest link, due to severe metal fatigue already set in, next time you may not be as lucky...
If it was me, ultimately, I would scrap the lot, making sure they were put beyond use...
If you go the repair route, have all 4 crack tested, and make sure that the worst wheels go on the rears, where they will do a lot less work....
Thom