Not quite what I meant, a blocking osc doesnt have to be a flyback, one side of a 12-0-12 would be the primary and the other side feedback to get the circuit oscillating.
However sounds like you allready have is sussed.
Your right about the mosfet gate, its a good idea to protect the gate with a zener or a mov in circuits like these, a few times I've had fets just go short due to the gates being overdriven, kind of annoying when they short gate to source and blow something else too.