The frame has a drain hole on the bottom.

 Sior is a nice cage. I'd simply use the Cervelo non-magnetic (really aluminum) screws, no washers.

Right, the degree of flush varies and is normal. Remember, the wedge makes the clamp wider (to clamp the post), and also taller (because of the ramp angle).

 Correct, only the Wolf SL was recalled. All the other Wolf fork models are okay: Wolf, Wolf TT and Wolf CL 

The 2013 S2 has a standard English threaded bottom bracket shell, aka BSA. So you simply buy a Shimano bottom bracket and install your crank. Threaded frames normally don't come with a bottom bracket. The internal cables are not fully lined, so plan a little extra time to fish them out. But it's not as bad as many internal frames. 

 There's only one length post, long, and it's expected most customers will need to cut some off.

 Not seeing where the seat tube angle differs?  73 on all sizes according to the chart, no? 

Rotor rings are good. But nothing beats Shimano. You can use the old technique: back off the power for a second as the chain climbs onto the new ring. 

I ride my bike. A dummy on a bike, even one who's not exactly like me, is more realistic than "no dummy" - which is very, very unlike me. 

Step 0: Do not remove the ring. Step 1: Remove the bolt - pulling the crank off along with it. Done! :-)