Thank you, this is fair, and we are treating it as a bug report against the tutorial. Short answers from the game's own rules:
Too many faces: every face adds firedamp to the air passing it, so the air leaving the last face in a row carries all of their gas. A face stops when that air is over 2 percent, so how many fit depends on how much air the road gets. SAFETY LAMPS in the shop show each face's firedamp before it stops.
A stopped face starts paying again by itself as soon as its air is good. Feed the furnace (F), or use a door to send fresh air to it before it passes the other faces.
The second shaft: the surface cannot be cut, so a shaft you dig stops one row short and no fresh air can enter through it. The SECOND DOWNCAST in the shop sinks a real one from the surface and brings in a second current.
Undo: doors, cloth and overcasts come down free with the same tool. Roads and faces stay.
Cloth: a heading is a road that ends blind, and air will not go up it on its own. Cloth hung where it meets a through road turns part of that current up to the face.
(Our replies here are written with AI help.)