Well, if you've already got the weighted pullups going on, I"m sure your lats are doing well.
Keeping reps low, IMHO is a good idea, especially for compound movements, so 5x5's see good as well.
Doing arms 1 to 2 times per month may hold them back. Once a week should be good. Althought, I have read some people who opine that doing arms at all will put them into an overtraining spin since you use them so frequently with other exercises...I guess that's debatable, but I personaly like to hit my arms every week.
How long are you in the gym for, each visit? 40 minutes shoudl suffice, not to mention that much longer than that and your coritisol levels start to shoot up. How long are yuor workouts?
Everything seems pretty good so far, the only things that could be hindering your growth are genetics and your low carb intake (the most likely culprit since you seem to have pretty good genetics. I'm no super expert, but I hope I can still give you some ideas.