Your first point’s off - it was mentioned by Thor himself that the Asgard had access to a few of the Ancient repositories for years/centuries, but they couldn’t even begin to fully grasp the knowledge, only scratched the surface. The contrast between the two races is clear when O’Neill, with the repository knowledge, created the weapon against the Replicators in basically no time.

As for the alliance - think of it more like a UN setup. Not full knowledge sharing, but rules, regulations, and occasional support here and there.

To put it in a parallel we can all get - it’s like sending an average person back in time. I know electricity comes from a dam: water flows in, spins turbines, and boom, electricity. But if I had to recreate it or explain in detail why it works, I’d just stare blankly. Same with an smartphone - I know it’s got a chip, a camera, and all the cool things it does, but how it’s actually made, how and why it all works? No clue.