I thought his behaviour was quite understandable. As you know all the other wizards as well are quite cold, bit grumpy, and distanced from theirs or anyone else's humanity. The wizard lady who was a smith was the same and she had a husband and a family, and knew some of her descendants. That's what few centuries of living does to a person. The dragon has seen 6 kings live and die. He was an orphan on the streets of some city and 3 years old when he discovered that he was a wizard, almost burning down the place trying to start a fire because he was cold and in rain, and he was taken to serve the capitol and the king. He had nobody to give him love, no mother or a father. No wonder he grew up distant and cold. In his mind he was on a mission to hold the Wood's influence, when he took those girls. He wasn't there to hold their hands.
I had no problem understanding his motivations, as a man who was so meticulous in his work and driven in his goals. I quite liked him. He isn't a dick at all imo, when you take all this into consideration.
As far as the romance with Agnieszka went, as I said I quite liked it. It developed gradually and was quite natural. Remember, she always says that doing magic with somebody is very intimate, it's letting a person see the real you, in a sense it's like being naked with someone and more than that. It's why she was hesitant to do the spell with Falcon.
When they did the summoning spell together, Agnieszka and the Dragon , she saw the real him, and I understood why she fell for him. I got it completely.
He's quite a tortured character imo, accepting of being a "bad guy" or a "dick" as you say, if it means stopping the Wood. That was all that was important to him. Unitil Agnieszka, when his becomes fascinated with her magic. Something he doesn't understand, anymore than he understands the Wood.