Beelzebub is shown as a deep thinker, again a reason to why he should be greatly respected. Milton does not use face to describe how he is but rather front. According to the Oxford English Dictionary, the front is in reference to Beelzebub's forehead, which is a sign of the perception that he has a vast intelligence and wisdom as seen through the eyes of those listening to his speech.
Engraven is a reference to "pillar of state" expounding on the point that Beelzebub is this central, stone post for the citizens of Hell. Beelzebub being the intellectual center of Hell. The stone faced seriousness of his "front" is also an alluded to through the use of the word engraven. The thought of Beelzebub as this serious, stone-faced being is another point Milton finds important to get across to the reader. Grave is imbedded in the word engraven, reminding the reader of Beelzebub's "grave aspect".
Beelzebub's deliberation shows how much more important his speech is than the other demons who have address Hell. While the other demons who have spoken simply get up and speak, Beelzebub's thought process is shown to us. Milton backs up how important Beelzebub's words will be with his actions. Just the action of thinking and rising for Beelzebub is a lengthy and serious process. As he rises to address the crowd, deliberation sits on his face. Milton again is throwing in a dichotomy of this demon who is "wise" with the true fact that he is a fallen angel.
Beelzebub is deliberating over the public care, over what will happen to the citizens of hell. Having digested what the others have said it is now up to Beelzebub, this high and revered demon to "save" the citizens of hell. The demons are presented as having an air of breathlessness as he is about to speak. The public "care" can also be the public worry by definition in the Oxford English Dictionary. Beelzebub is about to present a solution to this worry, something that unlike the other demons who have spoke, will be taken seriously.
-Erik Scott