Let's start with the LED driver. It won't work that way.

COMP should go to C4, FB to R1 and SW to L1. The PWM duty cycle is determined by the trimmer, i.e. the resistance ratio between charge and discharge. If you want a minimum duty cycle you would have to add an additional resistor to the charge path. For a minimum duty cycle of 25% that resistor should be 25% of the trimmer.