The first is probably most accurate if others are having it too, the second is also highly probable, either a your router couldn't handle it anymore (ours has done that before so we got a new one) or b it's hit like a point where it can't go on (RIP)i'd suggest calling up comcast, ask if there servers are being slow yadda yadda,
I have verizon, so I'm not sure if that helps the case or not
and I'm torrenting Xubuntu for my laptopand I'm getting these speeds lol, I'm not getting anything like whats happening to you
i was able to check bandwidth usage, i can assure it if there is a cap i haven't hit it