Interesting point on the sword on the back thing, never thought about it. Guess he needs his hands for sorcery more than the sword? Or simply not considered by the writer.
The later, IMHO. The sword (in a scabbard) was always carried strapped on the hip in real life. And this is the proper way to carry it even if you have decapitants on the belt.
Probably the first writer who put a sword on the back of his hero did not have a sword in his hands in his entire life but now it has become a genre cliche.
There is a lot of shit in the fantasy and "historical" novels about the improper use of arms and armor, like wielding a sword against full plate armor knights and chopping them into pieces. Pretty impossible thing to do (even for Conan the barbarian). The way to fight with sword against knights in full armor is not slashing and cutting (because it has no effect), but use the technics of grappling and halfswording and try to use the point of the sword in the gaps of the armor, etc.
Another crappy example is the extended use of ridiculous overweighted and oversized maces (like Gendry in last GOT season) when the real ones are light and small.
And another one: a knight in full plate armor with a shield in a battle. Why are you using a shield if you have full plate armor protection?
Those things totally ruin a scene for me.
It is very easy for a writer just read a little about warfare and combat technics in the Middle Ages to avoid this bullshit that destroys the suspension of disbelief.
I myself have real swords and real armor and I know what it is possible and impossible to do with them, an author (a writer or an illustrator) can easily obtain both too and so learn from direct experience. With that he could do a more consistent work later but it seems that nobody does that.