REQ-0003 through REQ-0007 (1.3 through 1.7): It is easier to verify an enumeration than "all", but I think it is sufficient to say that when deployed with a CCS, the Header Service will output a header for each image taken and announced via SAL.
REQ-0007 (1.7): Yes, WFS CCDs need headers during normal observing and calibration, and guider CCDs need headers during calibration.
REQ-0010 (1.10): The exposure time wouldn't seem to need any post-readout information. Any time delay after readout should be very short, as it is in the critical path for visualization, Summit analysis, and Alert Production. Nevertheless, with the end-of-telemetry event in REQ-0011 (1.11), it is the Camera's responsibility to minimize this interval, not the Header Service's.
REQ-0011 (1.11): The unique id is identically the OBS-ID from LCR-1424. If that is not unique, then there will already be other problems with persisting pixels. A detector id would only need to be added if a separate header file is written per detector. This decision is being evaluated.
REQ-0013 (1.13): The requirement will say for now that the Header Service output will be consistent with the data needed to generate a compliant FITS header. The details of the format to be used are being evaluated.
REQ-0014 (1.14): "hopefully" will be removed. The Header Service has complete control over the format of its configuration and can select YAML if desired, although consistency with afw.cameraGeom is desirable, which may suggest that some data should be in pex.config form.
REQ-0016 (1.16): FITS does not need to be mentioned here and will be removed.
REQ-0019 and REQ-0020 (1.19 and 1.20): I believe the original intent was for REQ-0019 to be a minimum list, with other potential content users or desired headers to be provided by the PST/Project Science Team.