Writing unfamiliar settings

To write the following scene I did extensive research into medieval life, castles, the history of the French province of Brittany, and Druidic lore. I joined the society for the preservation of Brehon, the Celtic language of Brittany. (It was easy to get caught up in the research.)

I am not expert at writing descriptive settings. I try to weave details into the action. I have to watch that I do enough to place the H/H in a scene.

Jermande wadded his shirt into a ball and headed for his aerie.
The back of Dinan castle was embedded in the ramparts, the massive earthwork wall that surrounded the 900-year old city and had defended its inhabitants from hordes of Romans, Franks, Gauls, and most recently, the English. Dozens of round stone guard towers were spaced along the fortification, but those on the bluff overlooking the river had fallen into disuse. Tenuous treaties and assassination had supplanted sieges and battlefield slaughter as the way wars were waged.
Tall, shaggy rows of hazel and berry brush thrived in the grassy yard between the sheer face of the castle and the armory. Once, this and all other arable tracts inside the fortress had been cultivated, thus guaranteeing a food supply in case the city was besieged by attackers or by quarantined by plague.
Curbing his impatience, he meandered through a small patch checking the ripeness of the tasty bramble fruits until he was certain that no one followed. Then he slipped behind the windowless armory and stepped through the shielding illusion he had set seven years ago around the base of the guard tower that was now his home. It was an elementary legerdemain, but simple spells were often the hardest to break.
He bounded up the circular stairs to his study.
“Greetings, milord.” His manservant spoke in the scratchy, oddly pitched lilt common to dwarfed men. Brion stood on a stool and, with the tip of his bodkin, deftly scraped droplets of wax off the surface of the writing table without disturbing the irregular pattern of small rocks and bird bones. “There is fresh water in the lave basin.”
“Brion, could I be alone with Angelique Valois without alerting my mother?” He poured a goblet of port and contemplated his divination spread from yet another angle.
“Do you plan to kidnap her a second time?” Brion’s reasoning was keen. “I was not in support of the first attempt.”
“Twould be thorny. Samat keeps a close watch on her charge these days.”
“Kaoc’h,” he cursed.
He climbed the steps to their sleeping loft and lifted up his goblet to a convergence of sunbeams that rayed in through the loopholes, the narrow vertical slits designed to rain arrows down on an attacking army. The rainbow colors that filled the room reminded him of the intricate, dangerous light fire mazes Longwy had created with his crystals.
All apprentices had to reason their way through them. The superficial burns healed quickly, but there was no way to complete the course without enduring at least one deep, scarring wound. The lesson was that a Brehon had to accept pain as willingly as progress, and to honor Celtic law over all other.

Ana