Your chicken will be done and moister at 163, and it will carry over those 2 degrees to 165. That's the magic number with chicken these days. USDA said we now buy better chickens.... Who am I to argue?
You can regulate it with either the concentration or by the time. I am pretty light on mine because I am lazy. I don't want to pile it all up in one day. I will brine for 24 then in the reefer for 24 (to dry), and the to the smoker. If I cut the brine concentration next I would be putting a fan on the bird to dry faster (it does work well), then I'd want to smoke it all the same day! That would start feeling like work. I like to open the reefer in the morning to get the cream for the coffee and surprise myself with what I can do that day! LOL
I can smoke my chicken on an electric at 275 after drying, and it will crisp. But its more like a paper skin.
Also even though salt does work in a brine better, the sugar works also. I usually so like 3/4 to 1/2, or 1/2 to 1/3 sugar to salt. And I have been really happy with my results. Good osmosis without over powering the natural flavors. Your aromatics of course are up to you, the brine is just the transfer medium.
BUT just think how lucky you are, now you have the perfect excuse to smoke again this week, and what you ate was still pretty tastee wasn't it? That is a win/win in my book!
Remember that its always a beautiful day when you can smell the smoke!