The white rabbit should keep stopping for you, leading you north and then turning west, to bring you to the source of the river between the fortune teller and the enchanter. You do not need to cross any water. If you get to the large rocks east of the fortune teller, you went too far.
The white chicken is in Bellegar's shrine closest to Casper. You can not get help for him; you can kill the chicken, or do nothing. If you decide to do nothing, you might want to save and kill the chicken anyway, to see what happens.
Keep exploring to find the other levers and
Parchment Scrolls. There is no rush on either.
The talisman of the south can also be found in the derelict tunnels (in a small chest in a tree in a goblin area; see
here). All 3
Talismans can be used in the correct order (save first) at a statue in the middle of the tunnels (a well lit statue, with a plant or something on either side, in the room at the top of the stairs down to the southern branch), to give you the Talisman of the North (which has +2 Wisdom, 3 enchantment slots and a couple other random bonuses).
