Even if he were able to withstand the blow, he wouldn't be strong enough to resist his brother's blows. He'd have to rely on his own strength, which is why he's so excited. He wants to know what he should do now that his brother is about to blow him out of the air. He asks his brother to tell him what to do, and the brother tells him that he'll owe him 100,000 cultivation points. The finger on his hand moves, but it's not his. It's the finger of his brother. He can sense the finger's movement, and he can tell that the finger is already depleted of its own strength. He tells his brother that he can sense his own genuine qi, and that's enough to break through the spell.