I've donated like 3 times to this project.

What I can't figure out is when I am not on Bandwidth tab the download speed goes down ... down ... down. As soon as I get back on the Bandwidth tab it goes up ... up ... up.

Why do I have to stay on the Bandwidth tab?

Do you have Peers/Pieces/Files set to show in the Transfer view?
If yes, have you tried to turn them off? (Layout option -> Peers/Pieces/Files -> Hide)