1) Yes it relates to Slat position corresponding to the Flap Lever position, if that is clearer than mud... remember that the QRH has to cover every possible flight phase and config, so..
If the Slats jam on retraction on the first part of a go-around in CONF FULL then the S > 3 line applies.
If the Flaps are jammed and the slats are working you land with the lever in CONF 3 so you use the S = 3 speeds.
2) Not sure about this - but would a leak in the APU fuel line use more than 600kg/hour (see definition of a similar rate)?