How do I wire a light switch that has 2 switches wired in but should only use 1?
Based on what you've been able to discern so far -- the black wire in cable #1 is from switch #1 and the red wire in cable #1 is from switch #2.  Cable #2 goes off to the other two kitchen lights and cable #3 goes off to the pot lights.

This means that for the configuration you want, connect:


the black from cable #1 to the black from cable #2 and the black from the light
the red from cable #1 to the black from cable #3
and all the white wires together.