Hey, I'm an applicant that will be entering school this fall, but I've done a fair amount of research on marketing careers, so I'll try to answer your questions (remember I'm not in brand mgmt yet, so please take my answers with a grain of salt). Those that are in the field and can confirm/refute, please do.
1. That's exactly what brand management is about. Advertising is a different function altogether and often doesn't require an MBA to get into.
2. IMO, marketing is a pretty good field to get into as it was not hit as hard by the recession as finance and, to an extent, consulting. Companies are always trying to figure out ways to move products and thus need marketing folks. In the case of many CPGs, the demand for food/drinks/household products can only decline so much, as many of those types of products are essential to daily living. A marketing MBA generally earns in the 90s-low100s coming out of school, which is a pretty good living. Not really in the same compensation ballpark as IB/MC, but still pretty good and with a work-life balance to boot. For verification on the numbers, check the employment reports of the schools you are applying to.
3. As a whole, and again this is just what I've heard, marketing is much less about prestige than finance and consulting, so it's much easier field to get into career wise. I'm not an admissions consultant so I couldn't really tell you how any of this would affect you getting into school, but I've been told that they look at applications holistically, so I don't have much of a choice but to take that at face value. Reputation-wise, Kellogg is obviously the best school as far as marketing is concerned, but Indiana and Wisconsin also have very strong brand management programs and ties to many companies for that function. I also believe that Michigan is pretty strong in this area as well.
Hope this helps!