Those cracks do not look like it is the heat that has caused them. They look to me like stress cracks.
I think you should talk to a reliable shipwright about how to fix it. I'm thinking a new
stove box, and line that with s/s sheeting, spaced 1/4" or so off the sides, but allow enough space for the stove/oven to gimbal. Sorry to say this, because it is a big job, but it look like the liner somehow came unglued, and the
boat has been moving separately from the liner.
See if you can get one of the guys here to take a look. I could be wrong about this. "Boatpoker" comes to mind. Send him a PM if he doesn't show up. Or leave a message on his Profile page.
Ann