So here is where things stand.
The issue the repair guy said was "100% postive is the problem" is the floor of the oven and flame defuser had fallen and was resting on the burner. Now he can't actually fix that because there is no boxed part to pull out and install. "Can you manufacture a bracket?" I say. "No, parts are not available" he says. $85 spent to understand the problem.
So off to Lowes. I bought so angle steel (weldable, not zinced) and some stainless fasteners. I would have preferred plain mild steel but well, no #8 pan head machine screws or sheet metal screws. Oh well.
I used the machine screws to put the two pieces of the oen bottom back together, being right respectful of the asbestos in the middle.
I cut off the angle steel to a foot. Drilled three holes and used sheet metal screws to mount it on the back wall of the oven. Put it in place and there ya go. I need my bolt cutters as the back screws extend just a tad far and it isn't level, yet. Those are at the boat so I will have to wait to level it.
Now the real question is turning it back on and testing. If this is the right solution we are good. But if we get another CO alarm the FD shows up and gets cranky with us. I looked for a hand held CO detector at Lowes but no go. The FD had a right nice one with them, but I don't need it that nice, I just need it workable and for an hour.
So for now it looks like we don't have to try to plan and execute a crash kitchen remodel. When you are under pressure the thing that goes up the fastest is the price. So I am happy with this, for now.
