Either $int_if is your wireless interface, or in /etc/pf.conf, add:
air_if = "ath0"
and
match out on $ext_if from $air_if:network nat-to ($ext_if)
For pre-4.7:
nat on $ext_if from $air_if:network to any -> ($ext_if)
Similar for ftp-proxy config, and include $air_if in your pass rules.