With drives larger than 1TB, go with RAIDZ2 if possible. 6x2TB gives you more potential for future expansion, but 4x_TB is fine if you're confident about how much storage you will need, and replacing 4 drives later to grow the pool is less costly than replacing 6.
Not correct. A read error during rebuild will result in data loss, not necessarily (nor even likely) loss of the entire pool.