See, that's the thing, "ordinary infallibility" is unenforceable, Catholics let each other disagree with ordinary infallibility all the time, which is why the right view is that inconsistency is everywhere. "Papal infallibility" is a retreat from the great 19th-century Protestant inroads on ordinary infallibility.

I think you're taking "consistent" sola Scriptura as if it teaches divorce from tradition, but it doesn't. If there were no traditional language one could make the glyphs mean anything one wanted. That is why Psalm 119 contains the individual Hebrew letters as part of the text, to show that language is important and nobody can understand any Scripture unless one has a cultural tradition informing the meaning of the words. From there C & P should agree that doctrine must be inferable from Scripture; John recognized that all that was needed to found sacred tradition had been written down. Catholics never say that any generation made up new doctrine not founded in Scripture, they always "discover" it as something the generations inferred from Scripture. The Reformers were about removing encrusted traditions that were not based in Scripture, starting with the idea that the Pope rather than Jesus absolves "all penalties" (postmortem "penalties" should be understood as limited to burning of stubble).

Apostolic succession, councils, and church history as you describe should be accepted by Protestants; all their chains of authority come ultimately from Roman Catholics (except those few pre-Protestant divisions coming from orthodox catholics). The councils are "infallible" except when they disagree or when one council throws out another as an anticouncil.

I suppose we might argue that OSAS was only enunciated later at Dort due to the hyper-Arminians (i.e. those who went beyond Arminius's teaching after he died but who are now called the standard "Arminians"). It's pretty much implied by Calvin's definition of predestination, but Dort dealt more heavily with the individual reflection experience on Augustinian perseverance (cf. Turretin). I'm pretty sure Catholics believe that there are special saints who had perfect assurance of eternal security. Yes, Lutherans taught fall from grace, and thus "evanescent grace", but I think that too is a result of the incompletions of assurance. To me OSAS is simply the unity of Paul's three tenses of deliverance; if you don't have assurance of deliverance in one tense you need to question it in the others, and if you have infallibility of deliverance in one tense (regenerational baptism) then you need to have it in the others. (The Reformation was a pushback for the abusive advantaging of doubt in the present tense.)

So I'd be happy to continue defending solas and OSAS as I define them, but we need to be very sure of the text of the doctrines we're debating because you recognize the subtle differences. I think we'd come out on the same side when the smoke clears.