Unless the government has specifically staked its continuing existence on the result of this vote, I would vote Yes. If it has, I might be tempted to abstain - but even so, the chances look to be a win for the Yes anyway. (Even a 40% turnout at 70% for the Yes = 28%, which validates the referendum). The best outcome would be a Yes victory but no government stand-down as a result.

I think referenda should, in any constitutional arrangement, be sparingly used. They can be manipulated and give rise to all kinds of complicated situations, as here. In any event, they should not determine the fall of the government, or they will constantly be abused to bring that about.