For that kind of damage, the shocks must have bottomed out or the car previously had air shocks and you've just opened up the old damage.
Regardless, the way to fix is weld with fish plate. Probably best to drop the gas tank for safety and better access to the crossmember. If the welder can get up there OK, you might not need to pull the rear end to access the area. Clean up the area for the welder to do their job might save a couple bucks.
The other option is to find another crossmember and have that welded in, but that's a lot more involved.
What brand adjustable shocks? Length, both collapsed and extended, makes a huge difference.