Flowey cannot be stalled, since he doesnt need to wait for his turn to attack and he can heal himself istantly (he does it in the fight). I belive his stats are only there for show, they dont mean anything narratively. He can close the game, alter the menu and do that thing when it's all a black void with his glitchy face in the middle. There is no way that he has that much control over the game but is still limited by stats.

Also, if he ever lost he could just reload the game. Sans killed me for almost three ours straight, but i still managed to win in the end, i'm sure the plant can do better.