Sorry i think i was unclear 
Talking about the ‘scales’ i pointed the towers and wall battlements.
in the following pic:
and according to the previous pics you posted with a toon in front of the castle gate, we can clearly see the battlements sourrounded in green are of the proper scale.
Aside this, the battlements surrounded in red look far too big.
Military achitects used to create battlements of 2 to 2.2m high for the merlons and 0.8 to 1.2m for the crenelles.
Making higher and bigger merlons would have been, aside beeing a waste of stone ( wich was a precious material at this time ), pretty unconvenient and asking for larger crenelles not protective enough for the castle defenders.
Though there are different battlement architectures along the ages, merlons and crenelles had a corresponding length of 2 and 1 for romans, up to 4 and 1 for later buildings ( like some in Carcassonne )
I guess there are many theories on this and many books written, but if you want some academic info for starting digging on this, you might be interrested in the french of XI to XVI century architecture from Eugene viollet le duc.
https://fr.wikisource.org/wiki/Dictionnaire_raisonné_de_l’architecture_française_du_XIe_au_XVIe_siècle
I don’t know wether or not there’s an english version of this though 
For the building techniques problem i saw, it’s just a matter of static mechanics applied to buildings.
Arches, always arches and only arches were the answer at this times 
For example, this:
in red, this long piece of wall laying over the void and carring arches over it, cannot exist.
This kind of ‘encorbelled’ ( not sure of the word though ) needs something under it for the weight charges to get down to ground, or at least it needs corbels.
Sorry am not familiar with all the english terms but if you need more info, i’ll try to find you some pictures 
I really love your stairs.png and door1.png.
Your textures are really amazing !
I really love all your work @gallifrey_falls !
Keep it up 
and happy blending ! 