He already went back in time once. He knows he’s not supposed to go back more than two hours a day, and while he breaks that rule quite often, he wouldn’t do it for something as minor as not wanting to wait until tomorrow.
If he was going to use the time turner again, he’d have just only gone a half-hour back from the beginning.
Knowing HJPEV, yes, he would have broken time within six hours. He wouldn’t have even had much trouble doing it.
And yes, there’s a stable time loop. It’s the one where he writes “DO NOT MESS WITH TIME”.
He already went back in time once. He knows he’s not supposed to go back more than two hours a day, and while he breaks that rule quite often, he wouldn’t do it for something as minor as not wanting to wait until tomorrow.
If he was going to use the time turner again, he’d have just only gone a half-hour back from the beginning.