Those rules only allows forwarding, it doesn’t cause forwarding. That is dictated by the routing table: that’s why we put that in POSTROUTING as well.

You need to make it so the packers are also routed to the right place. This can be done by changing the default gateway to be wlan0, or creating a secondary routing table, adding a rule to route eth0 packets through it. By default there’s only one, so if your server is configured to use eth0 as the default gateway, it’s where things will be masqueraded to.

This may help: www.allgoodbits.org/articles/view/24