1. In principle, starting values should not matter. In practice they often do. Sometimes you think the most likely parameter value is different from the prior mean. For example, the prior on the Calvo parameter often has mean 0.5, but in the posterior it will often be around 0.75. The estimated_param_init-block allows you to easily incorporate this. However, if you have no clue how to set this, then by definition your best guess is the prior mean/mode.
  2. If it works, you should not worry. Any starting value should work.

See also [Smet and Wolter DSGE for EU)