Your allegation (aka gratuitious assertion) that (apart from Scripture and Tradition), the Church is not guided by the Holy Spirit except in those of his judgements that meet the notes of infallibility ... is precisely what we're arguing about and you're simply begging the question.
Let me turn around my statement and re-phrase it into a question:
Is any (or has any) church doctrine, truth, dogma EVER been based on anything OTHER than Tradition/Scripture? No, because the Faith is based on Divine Truth, which can only come from these 2 areas.
Please point to one truth/doctrine that is outside of these categories.
That's utterly ridiculous and at the very least savors of heresy.
It's not heresy at all.
Perhaps 1% of the Magisterium in its entire history has met the notes of infallibility (that number is probably incredibly high).
You're speaking of the solemn/ex-cathedra magisterium being 1% of history. The rest of the Magisterium (which is still infallible) is based on Tradition/Scripture. You are minimizing the infallible nature of Tradition and "constant teachings" of the Church Fathers, Saints, Doctors, etc. This is "that which has always been taught" and makes up a large, large majority of the Faith (i.e. the simple catechism).
Your allegation that 99+% of the Magisterium can go corrupt and lead souls to hell is utter absurdity, and I would categorize it as at least implicitly heretical.
I've never said any such thing nor implied it. You just jump to this conclusion because a) you never engage in a rational debate, b) you won't be patient enough to listen to an explanation.
Using your %s just for the sake of argument, I would break it down as follows:
1% of Church doctrine = infallible, solemn pronouncements by the pope in ecuмenical councils and dogmatic decrees
50% of Church doctrine = infallible and clearly taught in Scripture, using a literal reading, as the Church commands.
49% of Church doctrine = non-solemn oral teachings from the Apostles, unanimously agreed on by the Church Fathers, preached and agreed on in every age by the saints, popes, doctors, bishops, etc. This would be called the ordinary & universal magisterium (truths believed "everywhere, always and by all"). This is all still infallible teaching.
One must distinguish between the Ordinary/CURRENT magisterium (i.e. current hierarchy of the day) vs the ordinary and universal magisterium (i.e. constant teaching of the Church since the beginning of time).
The ordinary/CURRENT magisterium/hierarchy can err if a) the pope doesn't teach solemnly, b) they don't teach "that which has always been taught".
So, yes, the CURRENT magisterium/hierarchy can totally err and lead souls to hell because Church doctrine is ETERNAL and not current. V2 modernists have been arguing for a "living magisterium" so they can claim that the CURRENT magisterium/hierarchy is infallible, but that's heresy. Outside of papal solemn decrees, The CURRENT magisterium/hierarchy is only infallible when it agrees with the universal/constant/eternal truths of Tradition/Scripture.
There is nothing in Church history that says the Current magisterium/hierarchy is protected from error
if they teach outside the parameters of solemn infallibility, infallible Tradition or infallible Scripture. These are the ONLY parameters that Christ gave the Church to be safe.