Well based from my mates care you should have a fan kick in around 98c , so that could be.something else to address.No definitely the fan wasn’t going very fast when it hit 109c. I can’t really say whether it opened before as I bought the car with head gasket fail as a do up car for the girlfriend.
In regards to the thermostat,
1) I would do check all connectors are connected properly.
2) I would think about, taking out the stat again and see if it opens manually like I tested in some cooking oil (obvious rig it so the electrical connector does not get covered in oil). I would possibly test your old one of you still have it also. If they open, I would look at rebleeding the system.
3) Maybe buy a block combustion tester to rule out it's not failed again, I've just bought one and testing tomorrow.
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