Interference from Bluetooth would affect the 2.4ghz band not the 5ghz band.
Your best use of a user forum is to ask which AC Routers people are using that work well with the Surface. Maybe that's a confusion point, this forum is not a Microsoft forum although there are some softies hanging out here.
We cannot write new drivers or firmware for either device. Even if we could point you to a sophisticated wireless diagnostic tool to analyze and identify the specific problem there isn't likely anything we can do to correct it, just confirm the existence of an issue. Most user based tools though are not going to reveal the underlying cause of the issue. It might require modifications to both devices before the issue is resolved over a period of months.
Bottom line: You just bought an Airport Extreme that's not working out, return it and get a different router that's known to work based on the collective knowledge of users. That's your quickest problem resolution path regardless of where the problem lies.