It little profits that an idle king...
So your first sentence is not an unheard of construction.
He little helps his friends.
This gives the suggestion that he provides help infrequently. It also sounds formal and literary.
He helps little his friends.
This sentence sounds like he's trying to make his friends smaller.
He helps his friends little.
This sentence could mean infrequently; it also sounds like he's just generally not of much help. It is less formal-sounding too.
This last one, I think we've all agreed, is probably the most common way of expressing what you are trying to say, although gmcgath is right in the comments, where he says that
He helps his friends very little.
is more usual.