SPNE and Pareto Optimality
Proof of "the SPNE of a sequential game might not necessarily be Pareto Optimal"?
I don't get it, your example is a proof of this statement. So what else do you need?

If you need another example, just take the prisoner's dilemma, and turn into a sequential game with imperfect information. Then, the NE is equal to the SPNE and you have an equilibrium without Pareto optimality