How is the switch current related to output current in a DC-DC converter?
The MC34063 datasheet actually tells you on page 11:
 $$I_{pk}(switch) = 2I_{out(max)}(\frac{t_{on}}{t_{off}}+1)$$

For more details, it points you to the OnSemi application note AN920A/D. I highly recommend reading these.  Also, Texas Instruments has some pretty good application notes regarding switching power supply design.

As an aside, you have under specified D1, it will see currents that are higher than 1A for sure.  Also, if you want good efficiency, be very careful with your layout.