Not suggesting we overhaul this, but what’s the logic with the Resistance and the Senate? The line for Leia saying that the Senate is their target, seems to beg the question of why the Senate does not seem to be warned or begin to evacuate.
My logic is: Evacuating a few hundred people from a military base would take a few hours and some transports.
Evacuating an entire solar system would take months and more ships than the Republic has.
Sure, just evacuating the Senate could work, and in a logical world they would be evacuated regardless of whether they know the weapon’s target or not. But perhaps Leia did tell them that there was a threat and they decided to trust Leia’s plan, or perhaps they would refuse to evacuate because it would prove that the Resistance was feeding intel to the Republic. Or maybe the easiest explanation is one supported by canon - almost half of the Senate is comprised of First Order sympathizers so they would reject any message from the Resistance, leading to delay and destruction.
JEDIT: In the deleted scene where Leia is appraised of the Senate’s actions, I could have Eddie record a line to the effect that the Senate is still in deliberations and refuses to even evacuate.