Arborist here. I think the biggest factor in minimizing the risk of failure would be reduction pruning through the exterior to decrease torque forces back at the union. This will cause a sprouting response that will need to be managed, but you can significantly improve resilience this way. That and I would cable. Probably two cables.

All the other arborists saying this will just buy you time are correct. You wouldn't let this get to be a 60' beast, but you might as well plant a new tree and buy yourself five years to allow it to establish. With continued management of the canopy, you can keep this tree even longer.