Reading Isaiah 6 - part 1

This is the famous chapter on Isaiah's commission.

Isaiah sees a vision of the Lord on his throne, with seraphs singing:
"Holy, holy, holy is the LORD Almighty;
the whole earth is full of his glory." (v.3)

The seraphs are no pretty delicate angels - they have six wings and at the sound of their voices the temple shakes and is filled with smoke. Wow!

Isaiah is struck by a sense of his uncleanless
"Woe to me!" I cried. "I am ruined [or undone] ! For I am a man of unclean lips, and I live among a people of unclean lips, and my eyes have seen the King, the LORD Almighty." (v.5)
Is his emphasis on his lips the knowledge that he cannot join the angels in their praise of the holy God (because he has sinned and is unclean)?

A seraph touches his lips with a live coal from the altar and pronounces him clean:
"See, this has touched your lips; your guilt is taken away and your sin atoned for [purged]." (v.7)
The coal is so hot that even the seraph has to use tongs! But with holy fire from the altar (where the sacrifice is made), Isaiah's sin and guilt is burned away.

Isaiah hears the "voice of the Lord saying, "Whom shall I send? And who will go for us?"
Who is the 'us'? Is it like the royal 'we'? Or is this some reference to the trinity?

And Isaiah, famously, says: "Here am I. Send me!"
No hesitation there...