Why specifically did Darth Vader choose Han Solo to test the carbonite freezing?

First Point: Availability of other options Given the size of the Imperial Fleet and the Super Star Destroyer alone that Darth Vader traveled on, there must have been some prisoners or disobedient stormtroopers or failed captains for Darth Vader to choose from. In addition, there could have been some non-compliant citizens or prisons in Cloud City itself to choose from. Therefore, why did Darth Vader choose specifically to put Boba Fett's bounty at risk instead of say, some anonymous character in the story?

Second Point: Respect for Boba Fett It's clear that Vader has some level of respect for Boba Fett, so when Boba Fett says "He's worth a lot to me", couldn't Vader have said "We will use prisoner X instead, possibly Leia or Chewbacca", instead of "The Empire will compensate you for your loss"? Or even put Chewbacca in for pushing those stormtroopers around in protest before Han was frozen.

See here for the scene in question.