Changing your MAC address will work out great if you're trying to hide from other people on your LAN or get around port-security on a Cisco Switch, but that MAC address doesn't leave your local LAN. It's layer 2, IP is layer 3. If you use a VPN it might actually leak that MAC address to the private network because of how the technology is designed. Using Tor to download torrent is discouraged because you're slowing down the Tor network and your privacy isn't even secure. I can show you a lecture on this topic by the IronGeek guy, but basically: Torrents are famous for being about as private as a glass house.
My recommendation is to operate a Tor exit out of your home and then simply torrent from your own network. This gives you plausible deniability because anyone can use your connection to do anything therefor you can't be held solely responsible for everything on your network. You're also granted immunity under the DMCA safe harbors clause. There is literary a template for responding to DMCA complicates filed against Tor exits on the Tor project's website.
If you want to remain anonymous and avoid abuse complaints:
Buy a seed box, which is basically a dedicated server with a torrent client running on.
Setup a Tor exit on that dedicated server.
Download to your heart's content.
If you'd rather not deal with all this work, I've been a system admin for as long as I can remember and I could easily set this up for you. In return for ether a price or access to the seed box. :3
Message me if you you'd like to talk.
