I read what the interwebs had to say. Some folks claimed welding a plate in the stove should be fine. Others recommended patching the cracks with furnace cement. These are both possible solutions but ultimately, they're not safe. Different materials will expand and contract at different rates. After a while, I would expect the welds or cement to fail. On top of that, if the firebox is cracking (its already warped), it means the stove has been over fired and damaged.
A cracked firebox can lead to several bigger problems. The cracks will allow air in and that means an uncontrolled burn. The cracks can also allow smoke out and that means possible carbon monoxide poisoning.
After all of the research and the unsafe conclusion, my family decided to retire the old stove. So...
RIP Blaze King KTJ-2000