Can you cast multiple Virtue spells on a target, giving him more than 1 temporary hit points?
No, that's a "same source" and so doesn't stack any more than multiple cat's grace or multiple hastes would stack.
It would overlap, so you could cast virtue on someone, then they take one point of damage, then you cast virtue on them AGAIN, they then take another point of damage, then you cast virtue on them AGAIN, etc.
You also have to wait 1 minute between casting virtue on any single target, because that's how long the spell lasts. It doesn't cease to function because the temporary hit point is now gone.
You also have to wait 1 minute between casting virtue on any single target, because that's how long the spell lasts. It doesn't cease to function because the temporary hit point is now gone.
Actually you can be affected by the same spell more than once. In that case your get the better bonus, which in this case is 1 temporary hp.
This does not allow stacking multiple virtue at the same time, as the rules for temporary hp says that temporary hp from different sources does not stack with each other, only granting you the highest bonus.