After reading two of the five pages of responses, it sounds like you are getting buried due to the bass settings the guitarist is using. Boosting your bass wouldn't help and although you probably don't need to pull it all the way down to 9:30, I think you are on the right track. The one area that the bass usually owns in the mix is around the 250Hz frequency. That gives you the thump and definition in the mix. Looks like the mid selector on your amp will boost/cut at 220Hz with your frequency selector on #1. With the selector on #2, it will hit around 450Hz, which is not what you need to boost.
I can't tell from the manual if that is a sweep selector or just offers you those 5 centers. if you are only offered the 5 mid frequency centers, I'd suggest you make SURE your "Ultra-Low" selector is off, run your treble EQ flat, drop the Bass to about 10:30; select #1 for your mid range and boost it to about 1:30. Give that a try to see if it doesn't help. If it's an actual sweep selector, just set it slightly beyond the #1 and that should get you to the 250Hz range. Really sucks when you have someone who won't listen to the overall mix of sound and insists on drowning everyone else out. Usually, bands like that don't get a lot of gigs because it's no fun to listen to that kind of sound.
Good luck!