Some LUNA Staking Questions

(1) Does anyone have the power to make Terra more secure simply by staking Luna with its validators.

If the answer to (1) is true

(2a) Would it be best that validators do not offer zero % commission if they make no money they would not care if people redelegate. Unless there is something else at play like losing their node? What other factors keep the node honest?

(2b) How does one choose the best validators/nodes to stake with? I would assume it be best to spread across a few DIVERSE nodes to help promote decentralization?