Now you're left having to explain why we need a leap year; as well as why entropy exists throughout the universe.
Leap years are needed because the earth's rotation (1 day) doesn't align with the earth revolutions (1 year) so at the end you have a partial rotation that if not counted would cause seasons to drift
Entropy is a description of the amount of order or randomness something has. Gen 1:2 would be a description of low entropy where as each created day gets more organized entropy increases. God introduces order (high entropy) to a system of chaos (low entropy), but 1:2 confirms that entropy was a pre-fall process. Our bodies for example are based on entropic systems in order to survive
Not to mention why we are sinners.
Sin is that which goes against God. We are innately sinful because we are not God.
And if the moon was created to rule the nighttime sky, why is there a time when it is out during the day (what we call "new moon")?
The earth has a rotation and the moon revolves around the earth. The two are not in sync thus the moon may be visible at different times during night or day sky.
Also, why is our magnetic field getting weaker? why is our moon receding from the earth at a rate of about 1.5 inches per year? why this and that?
The earth has a molten metal outer core which is responsible for it's magnetic poles. Because it's molten it moves through convection currents as well as the planets rotation that can naturally dift which may cause a pole reversal event. Leading up to this the dift may manifest as a weakened magnetic poles
The moon makes tidal forces on the earth that cause the earth to have increased drag and the moon increase energy. The increase engery causes the moon to increase its orbital speed which in turn expands its orbit.
The 6 days of creation are not really about these things, they can have broad agreement but there is no reason to think the pre-fall world had a different kind of physics than the post fall world. Entropy for example is a part of creation that can show us without outside intervention everything is moving towards chaos akin to a Gen 1:2 state. Spiritually speaking this is highly agreeable, we need to be under a constant influence of God to overcome spiritual entropy but if we ignore God we slowly fade away to oblivion, an everlasting death of sorts. But with Christ was have access to everlasting life and can over come entropic systems.
Day7 is opposite in all ways to Gen 1:2, contrasting light/darkness, rest/unrest, order/disorder, and broadly high/low entropy. With Christ we move to a more ordered state, without Christ we move to more disordered state and the creation account certainly shows us this process. That is the gospel message through entropic system.