The circuit is not fail safe. It is possible to fire the MOSFET if the Arduino pin is open.
The circuit should not be able to do anything unless all conditions of safety are met and all connections are made.
The safety switch should prevent the MOSFET from turning on under all circumstances. Preferably in series with the gate, and have a 1k R from the gate to gnd.
Base R should be around 10k so LED would not light.
Review the circuit and look at any way the MOSFET can turn on if any wire is broken or component damaged. The current circuit is not something I would rely on.
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