On an IFR Low Altitude Chart what does this symbol mean?
① - ICAO ID

As indicated, will be used for OCONUS airports only (overseas), e.g. Guam has a 4-letter ICAO designator:



② - Symbol with circle: Lighting


  An "L" following the elevation under the airport name means that
  runway lights are on during hours of darkness. A circle around the "L"
  indicates there is Pilot Controlled Lighting. A star beside the "L"
  means the lighting is less than continuous.


(Source)

This is part of the legend, but there is no lead line.

③ - ATIS available part-time

This is not the tower frequency (as your question seems to assume), but the ATIS frequency.

This information is not redundant, the ATIS may be available full time for an airfield open part-time. This is the case for Grand Junction Regional in the snapshot above.