Hi there, I'm Tim and will be assisting you today. I have over 15 Years as an Engineer and have been with eBay, DoD and many others. I will do my very best to help you. If you like i can offer remote access and a call.
I use WISP Myself here in Colorado...are you looking to do something with Centos that it's really not designed to do, you are more or less wanting to implement QOS and have torrents go to the bottom of the list i'm guessing. The problem with that is there aren't really exact port ranges for torrents, the usual is 6881-688, but many torrent apps randomize them so that they are harder to trace, and throttle. So since more often not the torrent ports are randomized, and you will end up throttling down other services you don't mean to. QOS is an all around bad idea in my and many other opinions as it causes more harm than good oftentimes. I gather you are running out of bandwidth, which is a common problem with WISP, and other types of ISPs.
It might be better to monitor those who use too much traffic and implement a max amount of tormenting allowed before they are either throttled or cut off. The problem you are having is one many ISPs large and small face.
On some of the high end Cisco Routers, they have some better ways of throttling some types of traffic, but even that is not perfect. Most ISPs just leave it wide open. Please let me know if you have any questions Spidey.
Spidey, I'm logging off for the night, and will be back tomorrow, let me know if you want to bounce some ideas back and forth. as far as blocking IPS, that's very easy to do, it's the allowing torrents time when they can run all out that is the problem.