The technological inconsistencies can’t be explained by trade. You might notice that the book mostly visits the ‘rich’ areas like Lenamare’s school and Freehold. Actually Lenamare’s school and the castle in Freehold are just the places that is described in most detail. The other might be the Veriga’s secret room and the ship. The poor areas and such is barely even mentioned, we don’t really know much about them. The most thing we could get from the book are from the culture of the rich.
As for paper. Yes for thousand of years people had made paper, but, even by machine, a sheet of paper take days to make. Ink isn’t also made with just a flick of the hand. Bookbinding (essentially sewing the pages together) isn’t really that fast either. Also, it is obvious that there is a very strong limitation in using magic; like it can’t be excecuted at great speed and the need for concentration. It is clear that the kind of magic in Astlan doesn’t lend well for production in masse especially of intricate things like bookmaking. It would have deplete their magical reserves very soon or fatigued their mind from constant concentrating. Imagine how mind numbing it might be for a wizard to ‘xerox’ a thousand page book and then turn it into a book.
Armor and space suit? Huh? An airconditioned armor does not a space suit make. Especially when space suit isn’t comfortable, restrict movement, and is no barrier agains a sword.
As for soldiers, what they wear might be of similar purpose. A candle and an LED light has similar purpose but I won’t say that they are of the same technological level. A chain mail and kevlar? You must be kidding me. Want your soldiers walk to Afghanistan in chain mail?
As for this backwater thing. As I just mentioned the most described in the book are the rich.
The poor people? I don’t really know much about them, except maybe that some soldier whip them when they are not able to pay their taxes. Of course they probably be using oil lamps or cressets instead of candles and those glowing globes. They might be binding their feet with rough cloth instead of wearing boots and high heels. They might be living in mud shacks with earth floor instead of ‘brick’ castles with parquet floors. I just don’t know. There is barely any mention of them.
As for the temperature in the Abyss. When Tom was in the “The Ripe Young Maiden’s Surprise” he made the comment about the temperature in the Abyss. It is about the temperature of boiling water. Even half the temperature of boiling point of water is still very hot. Storing chemicals in that temperature isn’t really advised, alcohol is one of them.
But please. These kind of things doesn’t really bother much my reading experience. Put them behind my mind