You assume he has to be God leveled to create the moon... he already split Juubi's chakra into the 9-Tailed Beasts.
You also have no proof that he kept some chakra....I'm going by what the manga states, "he unsealed Juubi and then made the moon" all in his old age.
Creating celestial bodies is a level of God. If he was truly so powerful, he wouldn't have died of old age. Pick up any story, any mythology; creation is synonymous with god hood. The manga doesn't need to illustrate it, because it is common sense.
Why is the Juubi in that statement in the first place? Why couldn't he create a moon without sealing or unsealing the Juubi? If Juubi was not a factor in moon's creation, then the statement would have been made without any implications to Juubi. Look at how only Yang chakra was sealed within Naruto. It means that meddling with tailed beasts chakra is possible, not an impossible.
You have no proof to back your claim that Hashirama or Madara (EMS + Rinnegan) are far below sage in his base form, as there is no proof in the manga to suggest it. All we know is that he was a sage, he split the ten tails and created moon. Now look at Madara. He wanted to be reborn with his non-edo form. Do you think he is stupid that he would want to take on the 10 tails and seal it within him if he was not sure about his own power? He had been planning this for decades and he missed this important detail? Oh snap, I am weaker than Juubi. What i was I thinking. Back to the drawing board Obito.
Come on...