I'm wondering about - as far as your particular offshoot - whether you still follow the other teachings of Armstrong.
I believe the current larger group has dropped the Arianism bits and I know you're keeping the Seventh-day teaching.
How about the Armstrong's Anglo-Israelism and Pyramidology? Is that gone for your group also?
First of all I would disagree that Armstrong created anything new. For example, most of the doctrine he espoused can be found in the writings of people throughout the centuries. For example, E.W. Bulling printed "The Companion Bible" in the late 1910's (I believe). It is essentially a study bible. His notes echo many of the doctrines that Armstrong later was led to.
Armstrongs greatest work was to publish and preach the gospel. I think his organization was effective in that regard, but was lacking in fulfilling the spiritual needs of those under his care. I don't think that was his fault, but was more of a function of people trying to gain power within the organization.
As far as beliefs, United publishes The United States and Great Britain in Bible Prophecy which does propose that the descendents of Israel exist today primarily as the people of Great Britain and the United States. I think it makes sense.
I wasn't aware that Armstrong embraced Pyramidology and don't recall ever reading about it either. In either case, United doesn't have any doctrine concerning it.
The booklet Fundamental Beliefs should address any other doctrinal questions you have.