I am usually connecting to the internet through VPN (Mullvad). Would it make sense to setup an exit relay to run whenever I can? I can forward one or two ports to my machine. My IP may change often and I might have to shut down the node when I need the bandwidth for something else. Also the bandwidth won't be much. I expect 40KB/s upload on average with bursts to 70 or 80.

Mullvad is obviously already receving a bazilion complaints about forum SPAM etc (thus I often find myself blocked from a few sites, having to solve captchas in many cases) so I guess they will see no diference.