what happened to the noch?
You could leave the 'noch' aus and still have the same meaning, but 'noch mehr' is very often used in this way. In a word-by-word translation 'noch mehr' would show up as 'even more'.
how about the es? the answer uses 'there' instead of it.
The verb group "es wären gewesen" can be changed back to Präsens "es sind" which took the place of "es gibt" (= there is). Both 'es gibt' and 'there is/are' are used as a fixed expression to talk about the presence of something or someone.