Could be I misread you.
You wrote:
The memo notes that Steele was 'a longtime FBI source' at the time he worked on the dossier, and that the DNC/Clinton campaign funded this research via a law firm. It does not say, and having searched a bit around I also don't see this anywhere else, that when Steele passed his dossier to the FBI, he had any instruction to do so from Clinton, the DNC or the law firm. Some sources explicitly say the opposite, that he decided to send his information to the FBI on his own volition. Is there any proof that Clinton or the DNC did in fact direct him to do so?
I took this to mean you were implying that since "I also don't see that he had any instruction to do so from Clinton, the DNC or the law firm", the FBI did not know where the dossier originated from and who paid for it.
On reread I guess you're saying they did know but it wasn't the DNC that pointed them to it. Though I don't see that as too important.