Can a stake pool take your ADA?

No — and the reason is worth understanding, because the mechanism is the whole point of Cardano’s staking design.

When you delegate, your ADA never moves. It stays in your wallet, under your keys. What you grant is the right for your stake to count towards a pool’s chance of being selected to make a block. The operator cannot spend it, move it, or freeze it. There is no transaction to reverse and no counterparty holding your funds.

That is the difference between delegating and depositing. An exchange offering staking takes custody — your ADA becomes their liability and you hold a claim against them. Delegation takes no custody at all. You keep the asset, and you can redelegate or spend at any time without asking permission.

Rewards work the same way. They are paid by the protocol directly to your address, not by the pool. A pool that vanished overnight would cost you the blocks it would have made. It could never cost you your stake.