He wanted to break through from the seventy-third to the eighty-first layer of the Netherworld in one go, but it wasn't an absolute necessity.
With his current strength, he could certainly break through several layers.
With each layer broken, his strength would greatly increase, as would his control over the laws of the Netherworld.
By then, when his other split entity re-entered the Netherworld, not only would both splits easily break through to the Peak Divine Realm, but with control over the much more powerful laws of the Netherworld, slaying those in the Peak Divine Realm would be as easy as slaughtering chickens and dogs.
Plus, with several more layers added to the Netherworld, he would have more time to battle the empires of the Acquired Divine Race, and even if those empires had some trump card they hadn't played yet, he would have sufficient strength and time to grind them down.