I was taught that the rhythm is only inégal when the motion is stepwise, so the eighths on beat 3& in your example would be straight. I didn't study the primary sources and took these points on my organ teacher's word, but if I remember correctly, where there is melody and accompaniment, the inégal can be omitted in the accompaniment, and if there is a figure such as an eighth and two sixteenths in the melody (in stepwise motion), it becomes dotted eighth with 32nds. It usually affects eighth notes, and I was under the impression that inégal between sixteenths is completely at the performer's discretion. Again, I haven't studied the sources and can't say whether this reflects current scholarship.

As I understand it (I am no authority) the interval doesen't matter - after all, in the above example, if you performed the stepwise notes with inegal and the larger intervals without, I would think it would sound rather silly/ Numerous written out examples of unequal eight note skips can be found.

Whether you think it sounds silly or not, that is the tradition - additionally, the inequality is much, much more subtle than 3:1.

Furthermore, the tradition specifically only applied to equal notes, so written-out dotted pairs would be automatically exempt and not pertinent to this particular convention.

Actually, there is no documentary evidence for double-dotting as a matter of course prior to the Galant, and certainly none to be connected to a "French Overture" style. It was a twentieth-century concoction by Arnold Dolmetsch based on unrelated snippets from Galant authors which was somehow supposed to form the foundation of a unified and consistent style.

Of course, in the Baroque the soloist enjoyed almost unlimited license to modify what was printed—but what specifically was printed was always very clear.

For this and similar matters consult French Organ Music in the Reign of Louis XIV.
This is a relatively recent and thorough study by David Ponsford (Cambridge).
The notes inegales occur only on the quickest note values in a given piece, and, as noted above, generally not on skips. Every organist should have Ponsford's book!

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We are not even to the age of Wagner. Louis XIV died in 1715. Couperin overlapped him but lived some years beyond him. Claude Balbastre was born in 1724, nine years after the death of Louis XIV. If I remember correctly - always more questionable with the passage of time - French music did not move into the Romantic era until Napoleon.

I meant to add the other day, before the inevitable distractions occurred... When the French Revolution started, it was about 50 years later before any French organs were once again built. Much can happen in 50 years and the new organs sounded nothing like the old ones. Music style had changed totally, as well.

True. The difference between the American and French Revolution is that the American Revolution wanted to build something better. The French wanted to destroy everything.