1) If I have the warslinger halfling alternate racial trait to reload a sling as a free action that needs two hands, can I do that and still use actions for which you need to have one hand free? It's just a free action after all.
Or does using your hand for one free action keep it from counting as free for the whole turn?
2) Does warslinger apply to the halfling staff sling as well as to normal slings?
1) Yes, your hand is free to do other stuff. Because reloading is a free action for you, its no time at all to reload. Also you reloaded on your turn, doesn't mean it has to be the final action of your turn.
2) Same as above counts for the staff sling as well. A weapon inspired by that one Staff weapon Tass used in Dragon Lance. Or least I think that's where its from.
does using your hand for one free action keep it from counting as free for the whole turn?
If you used that hand to do something that makes it not free, then it wasn't free what that thing was happening. It was free before you did that, and it's free afterward, but while reloading, it's not free.
Does warslinger apply to the halfling staff sling as well as to normal slings?
I think by pure RAW, probably not, but I also think that's really silly, since it's a halfling racial trait and they're the ones who made the sling staff. JJ agrees, which is awesome.