Port-forwarding on Android 2.3.6 wifi-tether using Port Forwarder app I'm having trouble port-forwarding connections from outside my network when tethering with my phone. I have a bad understanding of routers and networking in general, so please bear with me.

My Android device is the one directly connected to the Internet. To enable access to my computer from the outer world via the Android device, I'm currently using the free app called Port Forwarder and my phone is rooted so I have the authorization I need. The port on which I handle connections on the server is 80. Accessing the Server's IP address (inside the network) with &lt;local_ip.addr.ess.here&gt;:80 I can access it, so that works.

The problem is when I'm trying to access it from outside the network, the app tells me to set the source to 80, and the destination whatever it is (their example is 8080); of course I set it to 80 since that's what the server is listening to. So I try to access the server from outside using &lt;phone.public_ip.adr.ess&gt;:80 but it doesn't work.

As you have noticed, I've got no clue what I'm doing and finding guides has been difficult, even for standard routers. Has anyone successfully used this app and maybe could help me out? I probably left out important info because of ignorance, if so, let me know and I will update the question.
I am not sure which version you're running, here is my advice. The cause you're probably blocked, is due Android's firewall and strong Se-Linux policy. 

Since you have a full root access, you can get a shell with ADB, and check that. Type su - and it will get you into root. I am using TerminalEmulator, but you can use native one, if it is shipped with OS.

If I've understood you correctly, your phone acts like router in tethering mode. So this is needed to forward packets:
echo 1 &gt; /proc/sys/net/ipv4/ip_forward

See if that helps. Most likely, you'll need to play with iptables, allow port 80,443 on the tethering port. 
This is not complete answer, but it is too long to post as a comment.