1. "while" is ok. From a style point of view, perhaps "when" is better if the action of trying to steal was short i.e if we think of this crime as taking place at a particular moment in time rather than over a period of time. It would depend on how many gift packets (?) and how long the process took him. 2. If you had "and", then the minister did two things, "praised" and "called" (not calling). If we omit "and", then we have a participle clause which acts as an adverb modifying the whole preceding main clause. I hope that makes sense.