Depending on your isp speed plan, you can get up to over 200 KB/s from the magnet site. So it looks like the ISP to me. Speeds starting off ok but then suddenly going down to abysmal speeds is a sign of p2p bandwidth shaping. Who is your ISP?

Trying another p2p program would confirm it, but for me the magnet link is enough proof. And no, they very rarely tell you the truth that they're filtering your p2p bandwidth.

Unlikely to make a difference, but you can try changing the listening port to a no. between 49152 - 65535