Ok, I've made a few changes to the list.

I also discovered that I had mistakenly entered the weight for the brake pair as the individual brake weights...

Once the bike is built, the steerer tube will probably be cut down a bit, shaving a bit more off the total weight. Not that I'm much of a weight weenie, but ending up below 10 kg (22 lbs) is a definite goal. Might go with lighter tyres in the end, and complete bike weights are often quoted without pedals, so that brings it down to 9.5 kg (21 lbs). Which isn't that bad for a steel road bike.

I have another concern, though. The wheels. I've read a lot about how the WH-R550 are very prone to breaking spokes. I've gone with the WH-R561 wheels in my plans, but they don't look very different and they are about the same weight and price. Is the spoke breaking a matter of uneven and too-low spoke tension in the wheels? Because if that's the case, I could always put them in my truing stand and balance tension better.