1) Use the FSA cranks
2) RD cage length will depend on what cassette you want to run. The short cage 6700 Ultegra derailleur will clear 28 teeth. If it's a 10 speed chain you're fine unless it is worn out. Replace when stretched.
3) Nice pads like kool stops will improve braking over lesser pads. Your brakes are probably fine (Are they? Do you feel you have enough braking power?) Only reason IMO to run Ultegra brakes is if you want to entire group to match.
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