1. Yes, you can think of it that way if it helps - though it's not necessary.
"It's not A; it's B". There should be a semicolon, not a comma.
"When you meet one it's like I imagine it must be [like] when two Masons recognize each other across a crowded room."
[I imagine it must be like] when two Masons recognise each other.
Two Americans with an active sense of humour meeting must be like (I imagine) two Masons recognising each other.
Student or Learner