He needs a lot more practice sucking his daddy's cock. All that gagging noise woulda been a turn-off for me if I was his daddy. He couldn't even make daddy cum with his hand, daddy had to take over and finish himself. But he did swallow all of it like he was sucking on a cow's teat.
I think he's exaggerating or that's how he is. It wouldn't be my case if he was just gagging and puking.