Theologically the SDA is on the border between being a heterodox Christian sect and a “cult”. They are much closer to Biblical theology than the Mormons or the Roman Catholic Church, but they do hold onto some significant, unbiblical beliefs.
Regardless of that when most people think of a “cult” they are thinking of it from a sociological perspective. That is they are thinking of group that uses various forms of manipulation and coercion, including mind control techniques to exercise a great deal of control over its members.
From a sociological standpoint the SDA is not even close to being a cult.
I have a feeling that 1st century Christians would have a very different idea of "Biblical theology" than what you have.
There are quite a few SDA churches and their world headquarters in the DC metro area, and they also have a respected university and a hospital in the area.