Welcome Nerm!
Just a few things
Is this Arthur bloke going to be your character or are you planning on making another?
Also your empire seems a bit OP, which will be interesting to see battle against the coming darkness and other but I feel the need to tone it down nonetheless.
Heres what I suggest
Since it is a nation full of conqeuered people then it would have a reasonably high rebbellion risk among its various provinces.
Since your nation keeps on conquering, logically speaking it could literally not keep up supplying troops and making arms without sacrificing the rest of the economy. So your warmongering might have to slow down a little.
I might be looking too much into this so I will let Fallen and Cephyl be the final voice.
BTW Guns were being made in the 1500s :)
Anime_Freak