DNS only points names to addresses. It doesn't deal with ports at all.
While some registrars and DNS providers have what APPEARS to be a DNS "forwarding" service, really, what they are doing is running a webserver that redirects to your server in a frame.
I'm a bit unclear on just what you are trying to accomplish. Could you provide a bit more detail? (Use "example.com", etc.)
If the goal is to not show the content when just the IP address is used, then the previous responses are on-track. You can use mod_rewrite to filter-out requests that don't have the domain name provided in the HOST header.
If you want to completely deny that a web server is present, that will require some application-level firewalling. You will need a firewall appliance or software that can examine the HOST header and close the connection if it is empty or not what you are expecting.
If you want to have example.com:80 to to one IP address and example.com:8080 go to a different one - you can't. We are back to the fact that DNS doesn't deal with ports - only addresses.
You could, however, set-up your main site (if I am reading this correctly, you have a site at a web host, and another at home) to redirect requests to port 8080 to your home site. But, you are either going to have to redirect to the address, or set up a seperate domain or subdomain.
Any reason you don't want to have www2.example.com, etc.?
Unfortunately, I don't see a way to do this cleanly where the user is not going to be the wiser. You can make it a bit easier for them by providing a redirect from your main site. But once they arrive at your home site, they are going to see either an IP address:8080, www2.example2.com:8080, etc.
I am assuming you cannot use port 80, because your ISP blocks it. If that is the case, you might want to read their terms of service closely, and make sure you are not in violation. It is NOT wise to violate the TOS when you have irreplacable high-speed service - e.g. a cable connection. If your cable company cuts you off for a violation, the problem is in most places they have a monopoly, and you can't go to somebody else for equivalent service.