WOOHOO IT WORKS ITS FIXED!
The reason I couldn't upgrade the 2wire's firmware is because apparently bell changed the firmware upgrade page from "192.168.xxx.xxx/tech/upgrade.html" to "192.168.xxx.xxx/xslt?PAGE=UPGRADE1" in a recent (2012) secret firmware update.
I upgraded the firmware to one made by Qwest (someone said it has a better UI than the Singtel one), but there were no guides for setting up bridging mode in the Qwest firmware's UI, only for unlocked Bell and Singtel firmwares, so I was really guessing at most of it. I changed the VCI from 32 to 35 (no idea what that means or does, but a guide told me to), and I changed a bubble from "PPPoE" to "RFC 1483 Transparent Bridging", because it had the word "bridging" in it, and I wanted bridging.
No idea what RFC 1483 is, and I do not know the difference between transparent and opaque bridging, but it appears to have bridged.
Then I hooked the modem up to my shiny new Netgear N600 WNDR3700
router, selected PPPoE and entered in all my Bell user/pass info, and hooray! It works!But here's the important part:
I am downloading 3 different torrents at once, maintaining an average download speed of at least 700kB/s (70% of my max), I am currently connected to 73 peers all at once, and I am still able to post this message to you! HTTP is working perfectly, and it is able to use the remaining 30% of my bandwidth just fine!
Before, if I wanted to post this message or surf the web, I would have to turn off my torrent app, and then wait several minutes for the connections to die, before I could finally
Thank you all SO MUCH for your help, advice, and wisdom! I had no idea the 2wire was so terrible at handling multiple connections at once. I am curious, does anyone happen to know its actual limit? It seemed like it couldn't even handle more than a dozen or so concurrent connections.