Hi everyone,
To Hit: -4.
I think there is a feat somewhere in terms of using unusual things as weapons - broken bottle, split chair leg etc. - without penalty. I suppose this could also include a halfling.
Damage: 1d3 Subdual
However, should damage also be done to the halfling? Intuitively, I would say yes. However, you don't deal damage to a weapon when you hit something so theoretically, no damage to the Halfling. For flavor though, I'd say 1d3 Subdual to both.
Best Regards
Herremann the Wise