Transfer between Marunouchi Line to Shinkansen at Tokyo Station

Hello, I would like to answer about transfer in Tokyo Station when I have JR Pass. I will need to transfer from Marunouchi Line to Shinkansen.

How long should I spare to get to the shinkansen line from Marunouchi line? We will be walking with a 7 years old kid so we couldn't walk too fast.

If I have printed the reserved ticket for the shinkansen, which ticket I should insert/tap at the gate (i.e. JR Pass vs Reserved Ticket vs IC)?

Thank you very much.