I've no complaints with you assigning holdings, but I do have a few suggestions.
Defense (46): We could do a single castle for (40), or we could do a small castle (30) and a tower (10). I would vote for the single castle, since we occupy a relatively small geographic area.
Land (18): Hills (7) for the Mine we'll be buying, Hamlet (10), and Stream (1)? Alternatively, we could drop the hamlet and just pick up a second domain. We're in the Vale, but we're not acquiring Mountains, which could imply we're closer to the coast if we desired a coastline. We have a decent amount of options here, and I think the only one we know for sure is Hills. Here is my formal suggestion: We're situated north of Heart's Home, nestled in the foothills of the the mountains. Looking at the map in the core rulebook, we'd be right in the armpit of those mountains, where an unnamed stream flows through to the Fingers. Hills (7), Stream (1), Dense Woods (5), Road (5). Our population is small and lives either within the castle or in its shadow. A fresh stream flows from the mountains, almost directly through our stronghold, and down towards the Fingers. Dense woods crowd against our walls, as if to push us back up into the mountains. This is part of our high Defense. A road makes travel through the dense wood actually manageable, though it requires considerable upkeep. This also gives us the opportunity to give a name to those woods and to the stream.
Power (22): I imagine a small force of well-trained men-at-arms; probably no cavalry or navy given our proximity to dense forest, high mountains, and fortified defenses. The unit types that make sense for us, in my opinion, are Archers, Garrisons, Guerillas (specialized for forest), Infantry, and Scouts. My suggestion: Elite Archers are (10), Veteran Garrison is (7), Trained Scouts are (5). Having an elite unit means we get to give them some backstory. Elite means along the lines of the Unsullied or the Brave Companions. Our archers would be famous, and it is in line with our emphasis on defense. Last time we went to war, our house was badly damaged; I can imagine a lord of the house unwilling to make himself a desirable asset by sitting on a force of infantry or engineers or anything.
Wealth (21): A Mine is (10). We could either grab a second Mine (10), or we could snag an Artisan (10). The Artisan would give us one of the following: castle-forged weapons, more defense from our fortifications, or +1 House Fortune. Last option is a Maester (10), which gives us +3 House Fortune, the ability to communicate via ravens, and it opens the option up for a player to be the Maester. I vote Mine (10) and Maester (10).
As for motto, I like your premise DrZ, but we could streamline it: "Honor bends nor breaks" is grammatically correct, catchy, and makes you think about what it's saying.
In closing, I found a pretty sweet Westeros map:
http://gameofthrones.net/images/Westeros_Maps/map_of_westeros.jpg