Three questions to consider. First, assuming you leave the band (and I can't see how you wouldn't), can you still do the band's originals for the second date? That's important for strategery. You may not even be able to do the originals with a band of replacements under the original band name, although someone here surely knows the answer to that. Second, assuming you can't, do you have a set of traditionals and/or covers ready to perform? Third, is the ale house owner likely to care whether you're doing originals or common traditionals/covers as long as you entertain the crowd? 'Cause it kinda sounds like he might.I think I can. I'm going to ask the owner what he'd like me to do regarding the 11/22 gig. I contacted him today to let him know we're forced to be a duo tomorrow, and to make sure that that was ok. He has a little trepidation, rightfully so, but ok'd it. The sticky point is that this band is well-known, and these shows are booked under that name, so replacing everyone might not fly with the owner. Tough situation that I'll be very happy to be done with.
I'm still not getting how you're performing as a duo when the Queen gig is for all five, but that's okay, I probably just missed the explanation. I'm also surprised that any band leader would choose to jump genres to do a Queen tribute show without rehearsing; not my favorite band but they were not exactly known for the simplicity of their music. Pride goeth before a fall, and after the fall cometh a long hard winter - if there's any justice.
Best of luck - the best revenge is always a life well lived!