How to configure ettercap-ng's etter.conf to use sysctl instead of ipfw for sslstrip plugin to work on OSX Yosemite?

When I run ettercap-ng with

sudo ettercap -Tq -i en1 -M arp ///

I get the an error based on ipfw from the etter.conf file, like this:

WARNING: [/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_net_ettercap/ettercap/work/ettercap-0.8.0/src/ec_sslwrap.c:sslw_remove_redirect:500]

Cannot remove http redirect (command: ipfw), please edit your etter.conf file and put a valid value in redir_command_on field

My etter.conf file has changed like so:

the ec_uid and ec_gid equal to zero

arp_poison_icmp = 0

arp_poison_reply = 0

arp_poison_request = 1

These have been uncommented

redir_command_on = "ipfw add set %set fwd 127.0.0.1,%rport tcp from any to any %port in via %iface"

redir_command_off = "ipfw -q delete set %set"

I have read that ipfw is deprecated for OSX Yosemite and it uses pf, but since the error asks to put a "valid value in redir_command_on field" could I put a similar rule in place using pf?

How could the etter.conf file be read by ettercap+sslstripPlugin?

Could I put in another "valid value" and set the rule using pf in another terminal?

Should I install ipfw?