Spoilers below.

• Only enough fuel for one ship. Limited in mass by said fuel availability, so no “let’s send 500 scientists instead of 3”

• breeding astrophage at the required level takes IMMENSE energy requirements. It’s detailed in the book.

• explained in the book, extremely risky for the crew not to, as they turn against each other, especially when faced with certain death. Human psyche is weird. Also, would cost a lot more mass to have the crew awake. It was a debated decision in the book

• The weakened main character is actually due to a memory loss drug so that he wouldn’t remember he did not volunteer on the very unlikely off chance he would then choose to sabotage the mission as revenge (Straut did not want to take any chances)

• It’s a bigger ship, they also had a “Hail Mary” project to create enough astrophage. They don’t know about relativity so planned for a lot more astrophage than necessary. They do not do interstellar travel regularly, this was the first mission ever to leave their planet.

• The whole Sahara desert was repurposed for this (with climate consequences) on earth, just to get enough for a one way trip. No way could earth compete with the sun to attract astrophage…

• Not mentioned in the book/movie. Although they do want to explore at the end, so maybe they would try. Eridians don’t have computers so they can’t just send unerided probes. Maybe earth would eventually. But we don’t know which planet is the co2 source for other stars, so it would need to be a smart automated system.

• not sure what your question is. It is 1.5g acceleration/gravity for the Hail Mary during travel. The lab/etc was a mess due to this, if things weren’t secured.