The Herald website is to be commended for putting so much of the Adventist/early Bible student/Russell documents online.
The SDA still keep the 1844 date, hence their historical interest in the Miller Movement. There are two books by the SDA that are great religious history books. One is the Prophetic Faith of our Fathers, 4 volumes, and the other is The Conditionalist Faith of our Fathers. Storrs in mentioned in both, and , as I recall, C. T. Russell is mentioned in the latter.
The Russell/Adventist connection got lost. In the early years of the WT, there were references to other Adventist magazines, through the 1880s, and some of the letters printed were from Adventists or former Adventists. John Paton, a former Advent Christian minister and associate of Barbour and a contributor to the WT and author of Day Dawn, parted company with Russell around 1882, and founded his own paper. But they engaged in a paper war that lasted through the 1880s. They likely shared readers between them. The group was very small yet. Gradually the Adventist connections and tone of the early WT faded away. By the 1900s Russell and the WT had a broader focus and was reaching out to a mainstream audience. Although Russell referred to Stetson and Storrs, he did not label them Adventists. He credited Adventist preacher Jonas Wendell with restoring his faith in the Bible, but only mentions one chance meeting. Most importantly, he denied learning a single truth from the Adventists. And he denied that he ever was an Adventist. The JWs lost track of Russell. It is only in the last few decades that we can retrace these roots.
It is likely that Russell continued to have some association with the Advent Christian church in the Pittsburgh area after his initial encounter with Wendell. Stetson was the preacher there in 1871-1873 and this must have been when he influenced Russell in his beliefs, and Russell must certainly would have gone to hear him preach. Russell wrote about the disappointment of the 1873 time movement which he did not espouse at the time, so he must have had some acquaintance with them. Wendell in 1870 had written a book of proofs for the Second Advent in 1873, and Russell wrote that he was acquainted with the proofs, because in 1876 when he read Barbour's proofs, he recognized them. If Russell had no acquaintance with Adventists after his first meeting with Wendell, how did he know this?
A likely scenario: the Adventists located in Pittsburgh/Allegheny were themselves divided on issues and had an uneasy relationship, sometimes meeting together, and other times not. There are hints that there was a division among them, and a reunion under Stetson. At some point Russell parted company, whether after Stetson left in 1873, or with his assocation with Barbour in 1876. The disagreements that Russell mentions that he had with the Adventists could reflect the issues of disagreement among different camps of the Adventists there. Wendell likely gained followers to the 1873 time movement in Pittsburgh. Stetson appears not to have followed this. Stetson preached age-to-come views, and preached a view of restitution similar to Storrs. The Adventists were divided on this subject. Russell rejected the 1873 movement because they expected the burning of the world, instead of a change of dispensation, allowing the living at the time to live into the kingdom.
Another issue could have been the name. Some of the notices of the church say that it was an Advent Christian Church, a denominational name. But other notices, with Stetson, give the Church of God. Stetson's Advent Christian Church in Norwalk, Ohio was also called the Church of God. This might reflect that Adventists divided into two groups, maybe one meeting in Pittsburgh, and other in Allegheny.
So Russell's disagreements with the Second Adventists really are issues of controversy among the Adventists at that time, and shows that he fit into the post-Millerite Adventist milieu, whether he called himself an Adventist or not. Many others also refused the label.
BTW, Russell's true roots are in the Adventists, and not in anything Mason/occultist/Satanic. The Great Pyramid can be found in several Adventist papers. Direct historical connections can be traced between Russell and the Adventists, unlike much of what is found on the internet, which is based on unsubstantiated speculation.