Since all of your tell tell signs point to the fact that you DON'T have run-flat (no markings on the side of the tires, have a donut spare), the safest thing to do is to assume that you DON'T have run-flat and just move on. I've NEVER seen run-flats on SAVs/SUVs/SUTs...unless BMW is considering the X3 to be more of a "wagon" than a "cross-over".