Dear brother Mubashir,
Your post contains a very important question: "If a 9th century Hadith was in line with the Quran, would you conclude that it was actually said by the Prophet?"
You know our standpoint. Even if a Hadith agrees with the Qur'an, we may say that the exalted Prophet MIGHT have said so. It would be a folly to assert that he indeed said so since the Ahadith were written on HEARSAY centuries after Prophet (S).
Whenever I mention a Hadith, I prefer to say that reportedly the exalted Prophet said so and so.
Prophet (S) is reported to have said ...........
A report attributed to Muhammad (S) states that ......
A lifelong student