Limiting the current with the LM2679
In the datasheet the following is also stated


  The peak switch current is equal to a factor of 37,125 divided by RADJ. A resistance of 5.6 kΩ sets the current limit to typically 6.3 A and an RADJ of 8.25 kΩ reduces the maximum current to approximately 4.4 A. For predictable control of the current limit, TI recommends keeping the peak switch current greater than 3 A. For lower current applications a 3-A switching regulator with adjustable current limit, the LM2673, is available.


meaning that for a peak current lower than 3 A, a lower precision should be expected regarding the current peak detection.

As for the relationship between the switch and load current, there is some dependence on a couple of parameters and the mode of operation as follows:

Discontinuous Mode 





Continuous Mode 



Source

Since the the LM2679 can operate in both modes, DCM and CCM, I would say it is not straight forward to come up with a rule-of thumb for the peak current value. As long as the peak current was kep above 3A, your best option would be to follow the ratio set by RADJ.