Is this set enough for basic suspension and brake work?

18 pieces covers standard wrenches, sockets, and drivers. For suspension or brake jobs, check your vehicle's service manual for specific socket sizes and specialty tools you might need beyond this kit.

Can I use this storage box in my trunk without worrying about tools shifting?

The hard panel construction holds everything in place. Interior organization keeps pieces from rattling around during driving or off-road conditions.

Are the tools treated against rust or corrosion?

Finish details aren't specified in the product data. Store the set in a dry environment and wipe down after use in wet conditions to protect your investment.