^ Some really good answers there

A few other bits I'll add. As a CC custom build owner myself.

1 Not sure about the BB, not a bad idea to just sell it with the frame. Get a 105 BB and be done with it?
2 They should work well. Canti's are plenty good and easy to set up (i think)
3 Thomson post, the 330 is the safe bet, I have several my CC has a 330 set back. if you ever want to switch it to another bike it'll most likely be good, The short one might not and the long one is way over kill for most frames. I have a salsa clamp on one of my bikes that has a 27.2 post, sorry I cant remember the size, it's common though. my cross check frame came with the stock surly clamp and it's fine.
4 King Head set. Not everyone agrees, but IMHO they are worth it. All my bikes have them and I've never once adjusted or re-built any of them, one is over 20 years old.
5. Jag wire. They do the job well and come in many colors, don't over think it.
6. Im sure those are fine, I have Avid shorty 6's. Easy to replace pads, and adjust. they leave room for fenders and snow clearance. That bike is made for Canti's

Down the line
1. Sure, Sturdy wheels on the commuter / town bike make a lot of sense.
2. The nice thing about the cross check is that you can run almost any type of bar and be happy. (i have) The profiles seem great to start, but you can always switch later. I happen to Love the FSA wing pro compacts I have the widest ones they make.