Pass ethernet interface to iptables rule in ansible playbook

I'm writing a pretty simple ansible playbook for setting up our iptables firewall in centos. Here is the playbook I wrote:

---
- hosts: test
  remote_user: deploy
  sudo: True
  tasks:
  - name: Get iptables rules
    shell: /sbin/iptables -L
    register: iptablesrules
    always_run: yes
  - name: Add nginx iptables rule
    command: /sbin/iptables -I INPUT -p tcp --dport 80 -j ACCEPT -m comment --comment "Nginx_HTTP"
    when: iptablesrules.stdout.find("Nginx_HTTP") == -1
  - name: Add nginx ssl iptables rule
    command: /sbin/iptables -I INPUT -p tcp --dport 443 -j ACCEPT -m comment --comment "Nginx_SSL"
    when: iptablesrules.stdout.find("Nginx_SSL") == -1
  - name: Add postgres rule on ham0 interface
    command: /sbin/iptables -I INPUT -p tcp -s 0/0 --sport 1024:65535 -d 0.0.0.0/0 --dport 5432 -m state --state NEW,ESTABLISHED -j ACCEPT -m comment --comment "Postgres"
    when: iptablesrules.stdout.find("Postgres") == -1
  - name: save iptables
    command: service iptables save
  - name: ensure iptables is set to start at boot
    action: command /sbin/chkconfig iptables on

Everything works as expected although I'm sure it can be better. But my question is regarding the Postgres rule. I want to dynamically replace the destination address of 0.0.0.0/0 with the IP of a specific interface (ham0) on the target box. I'm assuming I can do something like ansible_ham0.ipv4.address to get the IP address. But I'm not sure how to pass that into the Postgress rule as a variable.

I'm reading the documentation and having a bit of a hard time with it. I'll keep researching but in the interim if anyone has an idea of how to do this, I'd really appreciate the help.