We acknowledge the quotes that can be found in early writings of Russel making such statements as in the 1889 quotation you supplied and this one I found in the 1881 WT where he refers to the FDS as "that 'little flock' of consecrated servants".However the WTS itself acknowledges the accepted beliefs during that time period in its own Proclaimers Book pg.143, par.1, where it says after the above 1881 quote:
Over a decade later, however, Brother Russell's wife publicly expressed the idea that Russell himself was the faithful and wise servant. The view that she voiced concerning the identity of the 'faithful servant' came to be generally held by the Bible Students for some 30 years. Brother Russell did not reject their view, but he personally avoided making such an application of the text, emphasizing his opposition to the idea of a clergy class commissioned to teach God's Word in contrast to a lay class that was not thus commissioned. {bold added)
In "not rejecting their view" he certainly contributed to the then-current belief in his being the FDS even if it was started by his wife. By not saying anything against that idea, he was in effect giving the impression that that was his belief also.Also on pg.626, par.2, the WTS states of the time after Russell's death that:Many who were sifted out at that time clung to the view that a single individual, Charles Taze Russell, was the "faithful and wise servant".....Particularly following his death, The Watch Tower itself set forth this view for a number of years. In view of the prominent role that Brother Russell had played, it appeared to the Bible Students of that time that this was the case. He did not personally promote the idea, but he did acknowledge the apparent reasonableness of the arguments of those who favored it. He also emphasized, however, that whoever the Lord might use in such a role must be humble as well as zealous to bring glory to the Master, and that if the one chosen by the Lord failed, he would be replaced by another. (bold added)
So even if Russell didn't say the words "I am the FDS" he certainly helped the idea to exist for a time even narrowing it down to saying "the one chosen", at one time, instead of referring to the FDS as a collective body. That it itself supports the claims that Russell accepted the belief he was the FDS, even though his earlier quotations say otherwise.