Excellent choice.

Trek tunes the Madones to ride basically the same regardless of carbon used. All are durable and strong. If weight doesn't matter, the 5.1 is a perfect choice.

A triple can give you excellent results if properly adjusted, just like a double. If you want a regular double you can buy larger chainrings to fit the smaller crank pattern. I would go with the compact and play with new cassette or new chainrings if you need to make a change. I really enjoy my compact.

Spoke counts guru's make me nuts. Bontrager makes excellent wheels. They have a 5 year warranty, and no weight limit - no one else comes close on either. RaceXLite are great all around wheels, the RaceLite, and Race are ok, but start getting heavier. I'm currently running RaceXLite-Aero with 16 spokes (f/r), no problems! I'm pushing 190 and have hit plenty of holes. I good friend toured cross country on a set of RaceLites - 0 problems and he pushes about 230 lbs. We also run Bontrager Tandem wheels on our tandem, 0 problems. Maybe 20 years ago, low spoke count = bad wheels, not anymore.