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Irrelevant.  He wrote this while investigating the matter, and the Holy Office ruling unequivocally stated that heliocentrism is contrary to Sacred Scriptures. 

Nonsense.  You yourself admitted that neither ruling was infallible and therefore irreformable.  This doesn't mean that one of them wasn't wrong, nor does it lead to sedevacantism.  Certainly the 1616 decision was closer to meeting the notes of infallibility, whereas the 1800 one clearly did not, as it did not teach anything that must be held by the faithful (the main note of infallibility).

According to Ott rulings of the Holy Office are not infallible:

With regard to the doctrinal teaching of the Church it must be well noted that not all the assertions of the Teaching Authority of the Church on questions of Faith and morals are infallible and consequently irrevocable. Only those are infallible which emanate from General Councils representing the whole episcopate, and the Papal Decisions Ex Cathedra (cf. D 1839). The ordinary and usual form of the Papal teaching activity is not infallible. Further, the decisions of the Roman Congregations (Holy Office, Bible Commission) are not infallible.

If we have to choose only one as right, then it makes more sense to me that the later decision revoked the earlier one.  A pope can change a non-infallible teaching from the past but a pope cannot bind future popes on non-infallible matters.

I say if there were proof that Jesus Christ did not change water into wine then one would have to doubt the wording of Scripture.

This is the logic that they make of Bellarmine's 1615 letter by omitting the rest of what Bellarmine said. It would mean this letter could eliminate a papal decree defined and declared one year later. It suggests that Bellarmine considered the 1616 decree was provisional and not a proper ruling on formal heresy:

(1) “That the sun is in the centre of the world and altogether immovable by local movement,” was unanimously declared to be “foolish, philosophically absurd, and formally heretical [denial of a revelation by God] inasmuch as it expressly contradicts the declarations of Holy Scripture in many passages, according to the proper meaning of the language used, and the sense in which they have been expounded and understood by the Fathers and theologians.”

if it is never proven that is.

If this is how you believe the Church rules on formal heresies then we can believe anything under the same 'if there were proof of the opposite then the Church will reverse its teaching.' Wow, not even the Protestants taught of that one.