First of all, I'd drop. I also wouldn't be comfortable in a combined program regardless.
Second, I think a lot of people are spinning this issue in a bad way.
Yes, the medical school you attend is less important than other factors in determining competitiveness for residency. This does not negate it completely. What's perhaps more important is that by foregoing application, you lose the freedom to possibly achieve your full potential. If completing a combined program locks in a spot for you in medical school, that's fine, but you're also stuck wondering if you could have attended that other school you like with a more attractive curriculum, opportunities, etc... There are differences in medical schools beyond the number in the USNews Rankings.
In my opinion, the sentiment of "it's all about just getting in!" can be taken too far on here, and people fail to realize that there will always be applicants that will end up with choices. Would you want to be one of these applicants when they end up foregoing the option to choose? Yes, you can argue that no one can be certain about anything, but at a certain point your odds make it justifiable. Without divulging the complete status of their grades/EC's/etc it is up to the student, and the OP, to determine for themselves if they have good enough odds. If you personally feel that you will be competitive enough to earn the choices you think you can get on the table, you have the right to choose application over a locked-in spot and not be ridiculed for it.
OP, if you think you would regret staying in, wait until you take the MCAT, and then if you are in range for your target schools, drop out of the combined program. Until then, play it like you don't have a spot locked in anywhere.