For the issue regarding DA about which Aterpster is quite correct can I quote Pans-Ops definition of decision-height.
Decision altitude (DA) or decision height (DH). A specified altitude or height in the precision approach or approach with vertical guidance at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.
Note the term initiated.
The allowance for dipping below the DA is to account for the change of aircraft path which takes a little time to change from descent to climb.
If you hear "minimums", decide then initiate the g/a your margins will be significantly reduced.
Best way of thinking about it is to immediately go-around at the minimums call unless you have evidence to the contrary.
p.s. apologies for thread creep.
