If you talking only about TCU1 vs. TCU2 imho no, for much less money you can get much more information and features with Garmin Edge device ... But with Comp Carbon big price difference is also because of carbon frame, if carbon frame is what you want then there is no cheaper option anyway ...
Specialized Global Warranty is very clear, you can claim your warranty as long as you have a proof of purchase, so this letter from your dealer must be some kind of a BS ...
Starting a ride with cold battery is a bad idea anyway. But by having bike/battery inside the house and going on a very cold weather ride, a neoprene battery cover/sleeve does help keeping the battery a bit more warm during the ride. I use this Basil Universal battery cover, but my tailor had to...
Then your setup should look exacly like this (keep in mind the arrow should point in the direction of rotor rotation, also the bolts should be long enough that there is 9-13mm of the thread engagement into the fork):
Zeb has 200mm PM so if youre running 220mm rotor you should fit 20mm PM adapter, if you have 200mm rotor you should mount caliper directly (without adapter). Also with cps calipers (for example Guide RE) you should use cup washers between caliper and adapter/pm...