First, it seems improbable that Salazar entrusted all his magical knowledge to the basilisk, if only because that would have been a ridiculous amount of magical knowledge.

Well, it's not like he had to teach the Basilisk a full Hogwarts curriculum; he only had to teach it what he knew that triggered the Interdict of Merlin, which is only the top whateverth percentile of his repertoire.

Salazar wouldn't have known which pieces of knowledge from his time were going to become lost,

Sure he could have. All he had to do was write down the most powerful stuff he knew in descending order until he got to the point where someone else started understanding what they were reading.

Also, there's no reason to believe that basilisks have perfect memories

The Basilisk may not have a perfect memory as an animal, but it "would be huge flaw in sscheme" if Salazar's magical Parseltongue knowledge was corruptible by the limitations of any old snake's brain.

Salazar was only responsible for part of Hogwarts. We don't know that he was at all responsible for the wards, only that he had admin access to them…. We also don't know that Godric didn't revoke said admin access after Salazar betrayed him and left

I think you're extending your computer analogy too far. Salazar didn't have a revocable password to the wards, he knew the magic that created them, and the rest of the Founders certainly did not have the power to revoke spells from the Source of Magic.

Don't get me wrong, I think we're meant to understand that Quirrell did smuggle in the troll as a small transfigured object that Dumbledore drew his circle around. But nevertheless, I think we should also assume until further notice that h̶e̶ ̶k̶n̶o̶w̶s̶ whoever got the basilisk's knowledge got the most powerful magic that Slytherin knew.

EDIT: Hedged my last sentence, since Chapter 102's horcrux information introduces potential ambiguity as to how Tom Riddle's knowledge has been propagated amongst his alter egos' bodies.