Reason for Permit: Why are you equipped with 4 quad laser cannons? (Psst.. go with "Self Defense")

As someone who deals with weapons that require permits and registration... the correct answer is, "All legal purposes."

If you use it in the Mid-Rim, Outer Rim, or Expansion regions, it might not raise a single eyebrow. But if you use "Self-defense" in the Core (or your ship is flagged out of the Core), you'll probably get some guff from customs officials and the like about you don't need weapons for self-defense in the Core because of how safe it is and that you must be some sort of brigand. And it gets even worse if you're flagged out of the Mid-Rim or Outer Rim and have the same explanation, because then you must be a brigand because you have an armed ship and you hail from a region where there are pirates and criminals and rebels!

(And, of course, on some planets, self-defense may not be viewed as a legitimate reason for possessing weapons, particularly not weapons powerful enough to destroy another starship, even if they are permanently attached to your own starship. In which case you get to deal with the extremely awkward situation of having your ship's weapons confiscated and potentially being put in prison.)

I've had some thoughts on the Date Convention, mainly Using the year that Palpatine established the Empire as Year 1 but keeping the standard months and day. I was thinking of using After Declaration(AD) or Year of the Empire/Emperor(YE) similar to Anno Domini or Before Christ or Common Era or Before Common Era. Any other thoughts or suggestions?

It would seem to me that depending on time period, you would want to either use the founding of the Republic (~1000 years ago) or the founding of the Empire. Or the Empire might use a Sith-based system. Although that wouldn't fit Palpatine's narcissism and the cult of personality he's built. Maybe the Empire uses a date based on Palpatine's birth. Who knows?

Beyond that we don't have anything concrete to go on. We don't know how many months are in a year, how many days or weeks are in a month, and we don't know what their names are. There's probably a third date system based on when the Jedi Order was founded.

And you'd want to keep track of all three, because the Imperial system is going to be the only one used in the Empire, while the rebellion will likely use the Republic and/or Jedi system in the places where they hold sway, and those outside of the Empire proper (such as the Hutts) might prefer the apolitical Jedi system (although using the Jedi system in the Empire would probably be a crime).

He stole the ship and destroyed the other prototypes.

Happily, the destruction of the other Firesprays may no longer be canon.

In any case, the Firespray is back in serial production and, per Edge of the Empire, it's one of the most common civilian ships in the galaxy (along with the YT-1300).